This is strange.  It is true that this function (a modular form) goes to infinity as t -> 0 from the right.
But should plotting it it do this?

    |\^/|     Maple 2019 (APPLE UNIVERSAL OSX)
._|\|   |/|_. Copyright (c) Maplesoft, a division of Waterloo Maple Inc. 2019
 \  MAPLE  /  All rights reserved. Maple is a trademark of
 <____ ____>  Waterloo Maple Inc.
      |       Type ? for help.
> version();
 User Interface: 1435526
         Kernel: 1435526
        Library: 1435526
                                    1435526

> exp(-Pi*t/3)^8*JacobiTheta3(Pi*(4*I*t+1)/2,
> exp(-12*Pi*t))^8/(exp(-Pi*t/6)^4*
> JacobiTheta3(Pi*(2*I*t + 1)/2, exp(-6*Pi*t))^4);
                 Pi t 8              Pi (4 I t + 1)                8
           exp(- ----)  JacobiTheta3(--------------, exp(-12 Pi t))
                  3                        2
           ---------------------------------------------------------
                 Pi t 4              Pi (2 I t + 1)               4
           exp(- ----)  JacobiTheta3(--------------, exp(-6 Pi t))
                  6                        2

> plot(%,t=0..4);
memory used=48.4MB, alloc=45.3MB, time=0.45
Execution stopped: Stack limit reached.

Here is a strange one...

1> /Library/Frameworks/Maple.framework/Versions/2019/bin/maple ; exit;
    |\^/|     Maple 2019 (APPLE UNIVERSAL OSX)
._|\|   |/|_. Copyright (c) Maplesoft, a division of Waterloo Maple Inc. 2019
 \  MAPLE  /  All rights reserved. Maple is a trademark of
 <____ ____>  Waterloo Maple Inc.
      |       Type ? for help.
> version();
 User Interface: 1435526
         Kernel: 1435526
        Library: 1435526
                                    1435526

> DE := (28*x + 44)*u(x) + (336*x^2 +
> 726*x - 12)*diff(u(x), x) + (144*x^3 + 396*x^2 - 9*x)*diff(u(x), x, x);
                               2               /d      \
DE := (28 x + 44) u(x) + (336 x  + 726 x - 12) |-- u(x)|
                                               \dx     /

                               / 2      \
             3        2        |d       |
     + (144 x  + 396 x  - 9 x) |--- u(x)|
                               |  2     |
                               \dx      /

> dsolve({DE,u(0)=2},u(x));
memory used=21.5MB, alloc=44.3MB, time=0.37
memory used=53.3MB, alloc=84.3MB, time=0.94
Error, (in dsolve) when calling 'property/ConvertRelation'. Received: 'numeric
exception: division by zero'

Presumably, the solution should be

u0:=2*HeunG((11 - 5*sqrt(5))/(11 + 5*sqrt(5)), 352/(9*(11 + 5*sqrt(5))^3*(-11 + 5*sqrt(5))^2), 1/6, 7/6, 4/3, 1/2, -8*x/(11 + 5*sqrt(5)));

(I get that by replacing coefficient 44 in DE with variable e44, solve, then substitute back e44 = 44.)

But maybe the problem is that this solution turns out to be an algebraic function:

u1:=2^(7/6)/(1 - 22*x + sqrt(-16*x^2 - 44*x + 1))^(1/6);

Here is a strange one...

1> /Library/Frameworks/Maple.framework/Versions/2019/bin/maple ; exit;
    |\^/|     Maple 2019 (APPLE UNIVERSAL OSX)
._|\|   |/|_. Copyright (c) Maplesoft, a division of Waterloo Maple Inc. 2019
 \  MAPLE  /  All rights reserved. Maple is a trademark of
 <____ ____>  Waterloo Maple Inc.
      |       Type ? for help.
> version():                                                                   
 User Interface: 1435526
         Kernel: 1435526
        Library: 1435526
> I0:=(x - 11)^(n)*x/(x^(n + 1));                                              
                                             n
                                     (x - 11)  x
                               I0 := -----------
                                       (n + 1)
                                      x

> I1:=(x - 11)^(n)/(x^(n));                                                    
                                              n
                                      (x - 11)
                                I1 := ---------
                                          n
                                         x

> is(I1=I0);                                                                   
memory used=2.5MB, alloc=40.3MB, time=0.14
                                     true

> Limit(I0,x=infinity)=limit(I0,x=infinity) assuming n::posint;                
                                            n
                                    (x - 11)  x
                          lim       ----------- = infinity
                     x -> infinity    (n + 1)
                                     x

> Limit(I1,x=infinity)=limit(I1,x=infinity) assuming n::posint;                
                                                n
                                        (x - 11)
                              lim       --------- = 1
                         x -> infinity      n
                                           x

This was in Maple 2019.2 ... but I had Maple 18 (from 2014) running here, and it does the same thing.

How strange is this: replace 11 by 10 (or less) and the error goes away.

The function hypergeom([2/3,2/3,2/3],[-1/3,4/3],z) has radius of convergence 1 and real coefficients.

But Maple tells me evalf(hypergeom([2/3, 2/3, 2/3], [-1/3, 4/3], 99/100),50);

is -138.999 + 0.0012 I
 

It should be more like −138.9962313171333091754979138344422738025

(Maple 18, version 991181)

---

G A Edgar

Who knows what Maple does wrong on this one?

Download sum.mw