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A108479 Diagonal sums of number triangle A086645. 2
1, 1, 2, 7, 17, 44, 117, 305, 798, 2091, 5473, 14328, 37513, 98209, 257114, 673135, 1762289, 4613732, 12078909, 31622993, 82790070, 216747219, 567451585, 1485607536, 3889371025, 10182505537, 26658145586, 69791931223, 182717648081 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

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

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

FORMULA

G.f.: (1-x-x^2)/(1-2x-x^2-2x^3+x^4); a(n)=2(n-1)+a(n-2)+2a(n-3)-a(n-4); a(n)=sum{k=0..floor(n/2), C(2(n-k), 2k)}; a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, C(2(n-2k), j)C(2k, j)}}.

CROSSREFS

Sequence in context: A175120 A239357 A106910 * A178441 A014742 A085411

Adjacent sequences:  A108476 A108477 A108478 * A108480 A108481 A108482

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Jun 04 2005

STATUS

approved

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Last modified July 9 05:46 EDT 2020. Contains 335538 sequences. (Running on oeis4.)