

A002018


From a distribution problem.
(Formerly M3652 N1485)


1



1, 1, 4, 33, 480, 11010, 367560, 16854390, 1016930880, 78124095000, 7446314383200, 862332613342200, 119261328828364800, 19415283189746043600, 3675162134109650184000, 800409618620667941886000, 198730589981586780813696000, 55800304882692417053710704000
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OFFSET

0,3


REFERENCES

H. Anand, V. C. Dumir and H. Gupta, A combinatorial distribution problem, Duke Math. J., 33 (1996), 757769.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Table of n, a(n) for n=0..17.


FORMULA

a(n) = n*(2*n1)*b(n)  n*(n1)^2*b(n1), b(n) = A000681(n).


MATHEMATICA

b[n_] := Sum[(2i)!*n!^2/(2^i*i!^2*(ni)!), {i, 0, n}]/2^n; a[n_] := n*(2n1)*b[n1]  n*(n1)^2*b[n2]; a[0]=1; Table[a[n], {n, 0, 17}] (* JeanFrançois Alcover, Aug 08 2012, after formula *)


CROSSREFS

Sequence in context: A296835 A002190 A101981 * A219504 A258180 A072754
Adjacent sequences: A002015 A002016 A002017 * A002019 A002020 A002021


KEYWORD

nonn,easy,nice


AUTHOR

N. J. A. Sloane


EXTENSIONS

More terms from David W. Wilson


STATUS

approved



