%I A005725 M2843
%S A005725 1,1,3,10,31,101,336,1128,3823,13051,44803,154518,534964,1858156,
%T A005725 6472168,22597760,79067375,277164295,973184313,3422117190,12049586631,
%U A005725 42478745781,149915252028,529606271560,1872653175556,6627147599476
%N A005725 Quadrinomial coefficients.
%D A005725 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A005725 L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 78.
%H A005725 T. D. Noe, <a href="b005725.txt">Table of n, a(n) for n=0..200</a>
%F A005725 Coefficient of x^n in (1+x+x^2+x^3)^n.
%F A005725 a(n)=sum(i+j+k=n, 0<=k<=j<=i<=n, binomial(n, i)*binomial(i, j)*binomial(j, 
               k)) - Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 06 2004
%p A005725 seq( sum('binomial(n,2*k)*binomial(n,k)', 'k'=0..floor(n/2)), n=0..30 
               ); # Detlef Pauly (dettodet(AT)yahoo.de), Nov 09 2001
%p A005725 a:=n->sum(binomial(n,1*j)*binomial(n,2*j),j=0..n): seq(a(n), n=1..25); 
               - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Feb 12 2007
%Y A005725 Sequence in context: A114487 A017934 A005510 this_sequence A079522 A024426 
               A034016
%Y A005725 Adjacent sequences: A005722 A005723 A005724 this_sequence A005726 A005727 
               A005728
%K A005725 nonn,easy,nice
%O A005725 0,3
%A A005725 N. J. A. Sloane (njas(AT)research.att.com).
%E A005725 More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jul 12 2000