0,3

Also number of 2-colorings of the vertices of the 6-cube having n nodes of one color.

The b-file shows the full sequence.

W. Y. C. Chen, Induced cycle stuctures of the hyperoctahedral group. SIAM J. Disc. Math. 6 (1993), 353-362.

H. Fripertinger, Enumeration, construction and random generation of block codes, Designs, Codes, Crypt., 14 (1998), 213-219.

R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1979.

R. W. Robinson, Table of n, a(n) for n = 0..65

H. Fripertinger, Isometry Classes of Codes

(Mathematica program from Robert A. Russell (russell(AT)post.harvard.edu), May 08 2007)

P[ n_Integer ]:=P[ n ]=P[ n, n ]; P[ n_Integer, _ ]:={}/; (n<0); (* partitions *)

P[ 0, _ ]:={{}}; P[ n_Integer, 1 ]:={Table[ 1, {n} ]}; P[ _, 0 ]:={}; (*S.S. Skiena*)

P[ n_Integer, m_Integer ]:=Join[ Map[ (Prepend[ #, m ])&, P[ n-m, m ] ], P[ n, m-1 ] ];

AC[ d_Integer ]:=Module[ {C, M, p}, (* from W.Y.C. Chen algorithm *)

M[ p_List ]:=Plus@@p!/(Times@@p Times@@(Length/@Split[ p ]!));

C[ p_List, q_List ]:=Module[ {r, m, k, x}, r=If[ 0==Length[ q ], 1, 2 2^

IntegerExponent[ LCM@@q, 2 ] ]; m=LCM@@Join[ p/GCD[ r, p ], q/GCD[ r, q ] ];

CoefficientList[ Expand[ Product[ (1+x^(k r))^((Plus@@Map[ MoebiusMu[ k/# ]

2^Plus@@GCD[ #r, Join[ p, q ] ]&, Divisors[ k ] ])/(k r)), {k, 1, m} ] ], x ] ];

Sum[ Binomial[ d, p ]Plus@@Plus@@Outer[ M[ #1 ]M[ #2 ]C[ #1, #2 ]2^(d-Length[ #1 ]-Length[ #2 ])&, P[ p ], P[ d-p ], 1 ], {p, 0, d} ]/(d!2^d) ]; AC[ 6 ]

Cf. A034188-.

Sequence in context: A056204 A091148 A009354 this_sequence A115331 A152663 A113561

Adjacent sequences: A034188 A034189 A034190 this_sequence A034192 A034193 A034194

nonn,fini

N. J. A. Sloane (njas(AT)research.att.com).

Edited by N. J. A. Sloane (njas(AT)research.att.com) at the suggestion of Andrew Plewe, May 11 2007