# [seqfan] Re: Sequence with a strange for OEIS conjecture

Sun Oct 9 22:38:21 CEST 2011

These days I was able to prove the following (a very strange for polynomials) representation for polynomials of A174531:
P_n(k)=c_n(k)*(2^(n+k-1)-R_k(n)/(2k-2)!!),
where c_n(k)=((n-1)/2)!*prod{i=1,...,k-1}(n+i)/(n+2i), if n is odd,
c_n(k)=(1/2)*((n-2)/2)!*prod{i=0,...,k-1}(n+i)/(n+2i+1), if n is even,
and R_k(n), k=0,1,..., are polynomials in n of degree k-1(for k>=1) with integer coefficients, defined by the recursion R_0(n)=0, R_1(n)=1, and for k>=1,
R_(k+1)(n)=4*k*(R_k(n+1)-R_k(n))+(n+4k)*prod{i=1,...,k-1}(n+k+i).

A few polynomials R's: 0, 1, n+4, n^2+11*n+32, n^3+21*n^2+152*n+384, n^4+34*n^3+443*n^2+2642*n+6144.

Are the latter polynomials  in OEIS?

Best regards,

----- Original Message -----
From: Vladimir Shevelev <shevelev at bgu.ac.il>
Date: Wednesday, September 28, 2011 10:14
Subject: [seqfan] Re: Sequence with a strange for OEIS conjecture
To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>

> Maximilian Hasler and Peter J.C. Moses sent me the following
> extension with the correction:
>
> {1, 1, 3, 4, 2, 4, 5, 25, 32, 3, 19, 32, 7, 77, 294, 384, 4, 52,
> 240, 384, 9, 174, 1323, 4614, 6144, 5, 110, 967, 3934, 6144, 11,
> 330, 4169, 27258, 90992, 122880, 6, 200, 2842, 21040, 79832,
> 122880, 13, 559, 10569, 110513, 664898, 2161848, 2949120, 7,
> 329, 6867, 79687, 533630, 1935048, 2949120, 15, 875, 23121,
> 352385, 3300120, 18813500, 60080304, 82575360, 8, 504, 14504,
> 241800, 2482832, 15542976, 54575616, 82575360, 17, 1292, 45458,
> 949688, 12710033, 110549708, 606539532, 1911575472, 2642411520,
> 9, 732, 27762, 627528, 9104601, 85954668, 512386668, 1756141872,
> 2642411520, 19, 1824, 82422, 2259024, 40822659, 499742256,
> 4119259508, 21958313376, 68505970752, 95126814720, 10, 1020,
> 49284, 1449048, 28137738, 370512540, 3287673896, 18879806352,
> 63499315392, 95126814720}

> I am very grateful to them! Now  I am sure that  P_n(0)=floor((n-
> 1)/2)!*4^floor((n-1)/2). Further, if n is even, then the
> coefficients of P_n do not exceed the corresponding coefficients
> of P_(n-1) and the equality holds only for the last ones.
> Although these statements have only status of conjectures...
>
> Regards,