• Convergence with product

    From Peter Luschny@21:1/5 to All on Tue Sep 26 06:39:17 2017
    restart;
    for n from 1 to 10 do product(1 - exp(-3*Pi*k), k=1..n): print(evalf(%,100)) od:
    product(1 - exp(-3*Pi*k), k=1..infinity);

    0.99991930048242969540076079496607565337604701848050587887793116\
    61874620768881558525000761137393119619

    0.99991929397054310783846071160943458949489722010393675884188157\
    72031677006591102859909094004128441835

    0.99991929397001760173579420925756466546613464451769578307221030\
    46217577981046063251917225329379286853

    0.99991929397001755932770524384215301951312111267396474761039494\
    20757198264951861082576558744213889585

    0.99991929397001755932428293152156543805216017938155162138450575\
    61250456780918293082240670461486937285

    0.99991929397001755932428265534261219172472361853070175691267253\
    46521158633329104110223861614216303137

    0.99991929397001755932428265532032468343467328512694304556439538\
    78114792276826418913831611248576903856

    0.99991929397001755932428265532032288484350643390064827565514682\
    19527120690353372085351014843732960367

    0.99991929397001755932428265532032288469836099442954308820325275\
    36799279287625628587601960477165670312

    0.99991929397001755932428265532032288469834928126260024016748022\
    44320939278639343076761038920987656959

    0
    ?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jfh@21:1/5 to Peter Luschny on Tue Sep 26 15:50:34 2017
    On Wednesday, September 27, 2017 at 2:39:18 AM UTC+13, Peter Luschny wrote:
    restart;
    for n from 1 to 10 do product(1 - exp(-3*Pi*k), k=1..n): print(evalf(%,100)) od:
    product(1 - exp(-3*Pi*k), k=1..infinity);

    0.99991930048242969540076079496607565337604701848050587887793116\
    61874620768881558525000761137393119619

    0.99991929397054310783846071160943458949489722010393675884188157\
    72031677006591102859909094004128441835

    0.99991929397001760173579420925756466546613464451769578307221030\
    46217577981046063251917225329379286853

    0.99991929397001755932770524384215301951312111267396474761039494\
    20757198264951861082576558744213889585

    0.99991929397001755932428293152156543805216017938155162138450575\
    61250456780918293082240670461486937285

    0.99991929397001755932428265534261219172472361853070175691267253\
    46521158633329104110223861614216303137

    0.99991929397001755932428265532032468343467328512694304556439538\
    78114792276826418913831611248576903856

    0.99991929397001755932428265532032288484350643390064827565514682\
    19527120690353372085351014843732960367

    0.99991929397001755932428265532032288469836099442954308820325275\
    36799279287625628587601960477165670312

    0.99991929397001755932428265532032288469834928126260024016748022\
    44320939278639343076761038920987656959

    0
    ?

    With Maple 2017 (X86 64 LINUX) I got a different result:

    product(1 - exp(-3*Pi*k), k=1..infinity);
    infinity
    --------'
    ' | |
    | | (1 - exp(-3 Pi k))
    | |
    | |
    k = 1

    evalf(product(1 - exp(-3*Pi*k), k=1..infinity),100);
    0.9999192939700175593242826553203228846983492803172770315323192841366570017\
    065263132093348972377771038

    but what surprised me was

    assume(s<1/2,s>0);
    product(1-s^k,k=1..infinity);
    product: "Cannot show that 1-s^k has no zeros on [1,infinity]"
    infinity
    --------'
    ' | | k
    | | (1 - s~ )
    | |
    | |
    k = 1

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Peter Luschny@21:1/5 to All on Sat Sep 30 05:42:20 2017
    With Maple 2017 (X86 64 LINUX) I got a different result:
    evalf(product(1 - exp(-3*Pi*k), k=1..infinity),100); 0.9999192939700175593242826553203228846983492803172770315323192841366570017\
    065263132093348972377771038

    OK, so they fixed the bug.
    By the way here you can see a nice expression for it: https://www.wolframalpha.com/input/?i=QPochhammer%5BE%5E(-3*Pi)%5D

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)