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A023865 a(n) = s(1)t(n)+s(2)t(n-1)+...+s(k)t(n+1-k), where k=[ (n+1)/2 ], s = (natural numbers), t = (odd numbers). 0
1, 3, 11, 17, 38, 50, 90, 110, 175, 205, 301, 343, 476, 532, 708, 780, 1005, 1095, 1375, 1485, 1826, 1958, 2366, 2522, 3003, 3185, 3745, 3955, 4600, 4840, 5576, 5848, 6681, 6987, 7923, 8265, 9310, 9690, 10850, 11270, 12551, 13013, 14421, 14927, 16468, 17020, 18700, 19300 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..48.

Index entries for linear recurrences with constant coefficients, signature (1,3,-3,-3,3,1,-1)

FORMULA

G.f.: x*(1+2*x+5*x^2) / ( (1+x)^3*(1-x)^4 ). - R. J. Mathar, Oct 04 2014

a(n)= (8*n^3+24*n^2+10*n-3-3*(2*n^2+2*n-1)*(-1)^n)/48. - Luce ETIENNE, Nov 21 2014

CROSSREFS

Sequence in context: A181507 A154934 A302872 * A024592 A203162 A240084

Adjacent sequences:  A023862 A023863 A023864 * A023866 A023867 A023868

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified May 23 12:38 EDT 2019. Contains 323514 sequences. (Running on oeis4.)