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%I #32 Jul 22 2022 16:43:18
%S 1,1,4,6,19,27,50,56,74,56,50,27,19,6,4,1,1
%N Number of binary codes of length 4 with n words.
%C Also number of 2-colorings of the vertices of the 4-cube having n nodes of one color.
%D W. Y. C. Chen, Induced cycle structures of the hyperoctahedral group. SIAM J. Disc. Math. 6 (1993), 353-362.
%D H. Fripertinger, Enumeration, construction and random generation of block codes, Designs, Codes, Crypt., 14 (1998), 213-219.
%D R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1979.
%H H. Fripertinger, <a href="http://www.mathe2.uni-bayreuth.de/frib/codes/tables.html">Isometry Classes of Codes</a>
%t (* From _Robert A. Russell_, May 08 2007: (Start) *)
%t P[ n_Integer ]:=P[ n ]=P[ n,n ];P[ n_Integer,_ ]:={}/;(n<0);(* partitions *)
%t P[ 0,_ ]:={{}};P[ n_Integer,1 ]:={Table[ 1,{n} ]};P[ _,0 ]:={};(*S.S. Skiena*)
%t P[ n_Integer,m_Integer ]:=Join[ Map[ (Prepend[ #,m ])&,P[ n-m,m ] ],P[ n,m-1 ] ];
%t AC[ d_Integer ]:=Module[ {C,M,p}, (* from W.Y.C. Chen algorithm *)
%t M[ p_List ]:=Plus@@p!/(Times@@p Times@@(Length/@Split[ p ]!));
%t C[ p_List,q_List ]:=Module[ {r,m,k,x},r=If[ 0==Length[ q ],1,2 2^
%t IntegerExponent[ LCM@@q,2 ] ];m=LCM@@Join[ p/GCD[ r,p ],q/GCD[ r,q ] ];
%t CoefficientList[ Expand[ Product[ (1+x^(k r))^((Plus@@Map[ MoebiusMu[ k/# ]
%t 2^Plus@@GCD[# r,Join[ p,q ] ]&,Divisors[ k ] ])/(k r)),{k,1,m} ] ],x ] ];
%t 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[ 4 ]
%t (* End *)
%Y Cf. A034188, A034190, A034191, A034192, A034193, A034194, A034195, A034196, A034197.
%Y Cf. A171872 and A171876. - _Robert Munafo_, Jan 25 2010
%Y A row of A039754.
%K nonn,fini,full
%O 0,3
%A _N. J. A. Sloane_
%E Edited by _N. J. A. Sloane_ at the suggestion of _Andrew S. Plewe_, May 11 2007
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