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A297474
Number of maximal matchings in the n-cocktail party graph.
1
1, 2, 14, 92, 844, 9304, 121288, 1822736, 31030928, 590248736, 12406395616, 285558273472, 7143371664064, 192972180052352, 5598713198048384, 173627942889668864, 5731684010612723968, 200669613102747214336, 7426773564495661485568, 289713958515451427511296
OFFSET
1,2
COMMENTS
A maximal matching in the n-cocktail party graph is either a perfect matching or a matching with a single unmatched pair. - Andrew Howroyd, Dec 30 2017
LINKS
Eric Weisstein's World of Mathematics, Cocktail Party Graph
Eric Weisstein's World of Mathematics, Matching
Eric Weisstein's World of Mathematics, Maximal Independent Edge Set
FORMULA
a(n) = A053871(n) + n*A053871(n-1). - Andrew Howroyd, Dec 30 2017
MATHEMATICA
Table[(-1)^(n + 1) (n HypergeometricPFQ[{1/2, 1 - n}, {}, 2] - HypergeometricPFQ[{1/2, -n}, {}, 2]), {n, 20}]
Table[-I (-1)^n (n HypergeometricU[1/2, n + 1/2, -1/2] - HypergeometricU[1/2, n + 3/2, -1/2])/Sqrt[2], {n, 20}]
PROG
(PARI) \\ here b(n) is A053871.
b(n)={if(n<1, n==0, sum(k=0, n, (-1)^(n-k)*binomial(n, k)*(2*k)!/(2^k*k!)))}
a(n)=b(n) + n*b(n-1); \\ Andrew Howroyd, Dec 30 2017
CROSSREFS
Cf. A053871.
Sequence in context: A351857 A341395 A072148 * A270063 A033169 A090410
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Dec 30 2017
EXTENSIONS
a(9)-a(20) from Andrew Howroyd, Dec 30 2017
STATUS
approved