A057966 - OEIS

A057966

Triangle T(n,k) of number of minimal 5-covers of a labeled n-set that cover k points of that set uniquely (k=5,..,n).

1, 156, 15, 14196, 2730, 140, 984256, 283920, 29120, 1050, 57578976, 22145760, 3407040, 245700, 6951, 2994106752, 1439474400, 295276800, 31941000, 1807260, 42525, 142719088512, 82337935680, 21112291200, 3045042000, 258438180

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

5,2

COMMENTS

Row sums give A046166.

LINKS

Table of n, a(n) for n=5..30.

Eric Weisstein's World of Mathematics, Minimal cover

FORMULA

Number of minimal m-covers of a labeled n-set that cover k points of that set uniquely is C(n, k)*S(k, m)*(2^m-m-1)^(n-k), where S(k, m) are Stirling numbers of the second kind.

EXAMPLE

[1], [156, 15], [14196, 2730, 140], [984256, 283920, 29120, 1050], ...; there are 15 minimal 5-covers of a labeled 6-set that cover 6 points of that set uniquely.

CROSSREFS

Cf. A035347, A057669, A057963-A057965, A057967, A057968(unlabeled case).

Sequence in context: A278432 A299829 A115466 * A247435 A299170 A112818

Adjacent sequences: A057963 A057964 A057965 * A057967 A057968 A057969

KEYWORD

easy,nonn,tabl

AUTHOR

Vladeta Jovovic, Oct 17 2000

STATUS

approved