Search: id:A005987
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%I A005987 M0562
%S A005987 1,1,1,2,3,4,6,8,12,16,22,29,41,53,71,93,125,160,211,270,354,450,
%T A005987 581,735,948,1191,1517,1902,2414,3008,3791,4709,5909,7311,9119,
%U A005987 11246,13981,17178,21249,26039,32105,39213,48159,58669,71831,87269
%N A005987 Number of symmetric plane partitions of n.
%D A005987 D. M. Bressoud, Proofs and Confirmations, Camb. Univ. Press, 1999; p. 
               134.
%D A005987 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A005987 R. P. Stanley, Theory and application of plane partitions II, Studies 
               in Appl. Math., 50 (1971), 259-279.
%D A005987 R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see 
               Corollary 7.20.5
%H A005987 T. D. Noe, <a href="b005987.txt">Table of n, a(n) for n=0..1000</a>
%H A005987 R. P. Stanley, <a href="http://www-math.mit.edu/~rstan/papers/comb.ps">
               A combinatorial miscellany</a>
%F A005987 G.f.: Product[ 1/(1-x^(2i-1))/(1-x^(2i))^Floor[i/2], {i, 1, Infinity} 
               ] (R. P. Stanley)
%o A005987 (PARI) a(n)=polcoeff(prod(k=1,n,(1-x^k)^-if(k%2,1,k\4),1+x*O(x^n)), n)
%Y A005987 Cf. A000784, A000785, A000786, A000219, A048142.
%Y A005987 Sequence in context: A018718 A036451 A046682 this_sequence A125895 A064428 
               A052810
%Y A005987 Adjacent sequences: A005984 A005985 A005986 this_sequence A005988 A005989 
               A005990
%K A005987 nonn,nice,easy
%O A005987 0,4
%A A005987 N. J. A. Sloane (njas(AT)research.att.com).
%E A005987 More terms from Wouter Meeussen (wouter.meeussen(AT)pandora.be). Additional 
               comments from Michael Somos, May 19, 2000.

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