bug in A107755

[Artur]

If  A107755 have bug that mean that also A108784 
<http://www.research.att.com/%7Enjas/sequences/A108784> have bug.
ARTUR

Maximilian Hasler pisze:
>> %S A107755 2,8,12,26,30,36,38,80,84,90,92,108,110,116,120,242,246,252,254,270,272,
>> %N A107755 Numbers n such that Sum_{k=1..n} Catalan(k) == 0 mod 3.
>> %Y A107755 Equals 2*A074938.
>>     
>
> This %Y is obviously wrong (A074938 = "odd numbers such that...", but
> here are multiples of 4).
> Indeed all elements of this sequence are even, but the halved sequence
>
> %I A000001
> %S A000001 1, 4, 6, 13, 15, 18, 19, 40, 42, 45, 46, 54, 55, 58, 60,
> 121, 123, 126, 127, 135, 136, 139, 141, 162, 163, 166, 168, 175, 177,
> 180, 181, 364, 366, 369, 370, 378, 379, 382, 384, 405, 406, 409, 411,
> 418, 420, 423, 424, 486, 487, 490, 492, 499, 501, 504, 505
> %N A000001 Numbers n such that Sum_{k=1..2n} Catalan(k) == 0 mod 3.
> %Y A000001 Equals (1/2) A107755.
>
> does not yet exist on OEIS.
> M.H.
>
> __________ NOD32 Informacje 2701 (20071204) __________
>
> Wiadomosc zostala sprawdzona przez System Antywirusowy NOD32
> http://www.nod32.com lub http://www.nod32.pl 
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>
>
>   




aj> From seqfan-owner at ext.jussieu.fr  Mon Feb 25 12:12:23 2008
aj> Date: Mon, 25 Feb 2008 11:12:43 +0100
aj> From: Artur <grafix at csl.pl>
aj> Reply-To: grafix at csl.pl
aj> To: Maximilian Hasler <maximilian.hasler at gmail.com>
aj> CC: "N. J. A. Sloane" <njas at research.att.com>,
aj>         Sequence Fans <seqfan at ext.jussieu.fr>
aj> Subject: Re: bug in A107755
aj> 
aj> If  A107755 have bug that mean that also A108784 
aj> <http://www.research.att.com/%7Enjas/sequences/A108784> have bug.
aj> ARTUR

I've submitted an explicit change request to the sign of a(34) there,
which is the only error I detect in A108784:

> From oeis at research.att.com  Mon Feb 25 12:44:51 2008
> Date: Mon, 25 Feb 2008 07:44:45 -0500
> From: The On-Line Encyclopedia of Integer Sequences <oeis at research.att.com>
> To: njas at research.att.com
> Cc: mathar at strw.leidenuniv.nl
> Subject: COMMENT R. J. Mathar A108784
> Reply-to: mathar at strw.leidenuniv.nl
> 
> The following is a copy of the email message that was sent to njas
> containing the comment you submitted.
> 
> All greater than and less than signs have been replaced by their html
> equivalents.  They will be changed back when the message is processed.
> 
> This copy is just for your records.  No reply is expected.
>  Subject: COMMENT FROM R. J. Mathar RE A108784
> 
> 
> %I A108784
> %S A108784 1, 1, -1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, -1, 1, 1, -1, -1
> %C A108784 [swapped the sign of a(34) as already remarked by Noe in June 2007 in %E. Added Maple]
> %p A108784 A000108 := proc(n) option remember ;
>         binomial(2*n,n)/(n+1) ;
> end:
> 
> A107757 := proc(n) option remember ;
>         local a;
>         if n = 1 then
>                 3;
>         else
>                 for a from A107757(n-1)+1 do
>                         if add(A000108(k),k=1..a) mod 3 = 2 then
>                                 RETURN(a) ;
>                         fi ;
>                 od:
>         fi ;
> end:
> A107755 := proc(n) option remember ;
>         local a;
>         if n = 1 then
>                 2;
>         else
>                 for a from A107755(n-1)+1 do
>                         if add(A000108(k),k=1..a) mod 3 = 0 then
>                                 RETURN(a) ;
>                         fi ;
>                 od:
>         fi ;
> end:
> 
> A108784 := proc(n)
>         A107757(n)-A107755(n) ;
> end:
> 
> seq(A108784(n),n=1..120) ;
> %O A108784 1
> %K A108784 ,sign,
> %A A108784 R. J. Mathar (mathar at strw.leidenuniv.nl), Feb 25 2008
> RH 
> RA 192.20.225.32
> RU 
> RI