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A026657 Sum{T(i,j)}, 0<=i<=n, 0<=j<=n, T given by A026648. 1
1, 3, 8, 18, 40, 84, 182, 378, 814, 1686, 3626, 7506, 16138, 33402, 71810, 148626, 319522, 661314, 1421714, 2942514, 6325906, 13092690, 28147058, 58255794, 125240050, 259208562, 557254322, 1153345842, 2479497394 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..28.

Index entries for linear recurrences with constant coefficients, signature (1,4,-4,2,-2).

FORMULA

G.f.: [(1+2x)(1+x^2)]/[(1-x)(1-4x^2-2x^4)]. - Ralf Stephan, Apr 30 2004

CROSSREFS

Sequence in context: A335464 A026635 A135094 * A036384 A294591 A080692

Adjacent sequences:  A026654 A026655 A026656 * A026658 A026659 A026660

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified October 24 18:08 EDT 2021. Contains 348233 sequences. (Running on oeis4.)