[seqfan] Re: Number array not found in OEIS
Vladimir Shevelev
shevelev at bgu.ac.il
Sat Aug 27 16:31:36 CEST 2011
I decode over rows (without the signs): a_1(n)=1; a_2(n)=2^n-1; a_3(n)=(2^n-1)^2 - 2*(2^(n-1)-1);
a_4(n)=(2^n-1)^3 - 16*(2^(n-1)-1)^2 + 4*(2^(n-1)-1);
a_5(n)=(2^n-1)^4 - 88*(2^(n-1)-1)^3 + 132*(2^(n-1)-1)^2 - 94*(2^(n-1)-1),...
Thus it is natural to expect that a_k(n)=(2^n-1)^(k-1)-P_(k-2)((2^(n-1)-1), k>=2,
where P_(k-2)(x) is a polynomial of degree k-2 with integer and alternating coefficients.
Regards.
Vladimir
----- Original Message -----
From: Richard Mathar <mathar at strw.leidenuniv.nl>
Date: Saturday, August 27, 2011 15:30
Subject: [seqfan] Re: Number array not found in OEIS
To: seqfan at seqfan.eu
>
> http://list.seqfan.eu/pipermail/seqfan/2011-August/015257.html says
>
> gh> From seqfan-bounces at list.seqfan.eu Sat Aug 27 09:32:33 2011
> gh> Date: Sat, 27 Aug 2011 00:22:57 +0200
> gh> From: Gottfried Helms
> gh> Subject: [seqfan] Number array not found in OEIS
> gh>
> gh> I came across this number array (should be extended to
> infinity) by q-brackets/q-binomials
> gh> to base 2 and cannot find a good description. Does
> someone know this array or has an
> gh> idea how to decode?
> gh>
> gh> 1 -
> 1 1 -1 1 -1 1 -1
> gh> -1
> 3 -
> 7 15 -31 63 -127 255
> gh> 1 -
> 7 43
> -211
> 931 -
> 3907 16003 -64771
> gh> -1 15 -
> 211 2619 -26251 234795 -1985131 16323819
> gh> 1 -31
> 931 -26251
> 654811 -
> 13255291 238658491 -4050110011
> gh> -1 63 -
> 3907 234795 -
> 13255291 662827803 -26961325147 973958217435
> gh> 1 -127 16003 -
> 1985131 238658491 -
> 26961325147 2699483026843 -220115609012251
> gh> -1 255 -64771
> 16323819 -4050110011 973958217435 -220115609012251
>
> I guess, up to signs, with offset 0 in both indices, the second
> column is
> T(n,1) = A000225(..)
> the third
> T(n,2) = 2^(2n+2)-6*2^n+3 = 3-6*2^n+4*4^n.
> the fourth
> T(n,3) = 2^(3n+3)-28*4^n+42*2^n-21 = -21+42*2^n-28*4^n+8*8^n
> the fifth
> T(n,4) = 420*4^n-630*2^n-120*8^n+2^(4*n+4)+315
> etc. So each column is a sum over powers of 2.
> Apparently T(n,k)=T(k,n) (mirror symmetry along the diagonal).
>
> Recurrences down each column appear to take the coefficients in
> A158474:T(n,2) = 7*T(n-1,2)-14*T(n-2,2)+ 8*T(n-3,2)
> T(n,3) = 15*T(n-1,3)-70*T(n-2,3)+120*T(n-3,3)-64*T(n-4,3)
> T(n,4) = 31*T(n-1,4)-310*T(n-2,4)+1240*T(n-3,4)-1984*T(n-
> 4,4)+1024 *T(n-5,4)
>
> Richard J. Mathar
>
>
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>
> Seqfan Mailing list - http://list.seqfan.eu/
>
Shevelev Vladimir
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