Search: id:A005726
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%I A005726 M1643
%S A005726 1,2,6,20,65,216,728,2472,8451,29050,100298,347568,1208220,4211312,
%T A005726 14712960,51507280,180642391,634551606,2232223626,7862669700,
%U A005726 27727507521,97884558992,345891702456,1223358393120,4330360551700
%N A005726 Quadrinomial coefficients.
%D A005726 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A005726 L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 78.
%F A005726 a(n)=sum{k=0..floor(n/2), C(n, k)C(n, 2k+1) }. - Paul Barry (pbarry(AT)wit.ie), 
               May 15 2003
%F A005726 a(n)=Sum[(-1)^k binomial[n,k] binomial[2n-2-4k,n-1],{k,0,Floor[(n-1)/
               4]}]. - David Callan (callan(AT)stat.wisc.edu), Jul 03 2006
%p A005726 for n from 1 to 40 do printf(`%d,`,coeff(expand(sum(x^j, j=0..3)^n), 
               x, n-1)) od:
%Y A005726 Sequence in context: A132353 A052958 A053730 this_sequence A148473 A000718 
               A148474
%Y A005726 Adjacent sequences: A005723 A005724 A005725 this_sequence A005727 A005728 
               A005729
%K A005726 nonn,easy
%O A005726 1,2
%A A005726 N. J. A. Sloane (njas(AT)research.att.com).
%E A005726 More terms from James A. Sellers (sellersj(AT)math.psu.edu), Aug 21 2000

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