

A054780


Number of ncovers of a labeled nset.


2



1, 1, 3, 32, 1225, 155106, 63602770, 85538516963, 386246934638991, 6001601072676524540, 327951891446717800997416, 64149416776011080449232990868, 45546527789182522411309599498741023, 118653450898277491435912500458608964207578
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OFFSET

0,3


COMMENTS

Also, number of n X n rational {0,1}matrices with no zero rows or columns and with all rows distinct, up to permutation of rows.


LINKS

Table of n, a(n) for n=0..13.


FORMULA

a(n) = Sum_{k=0..n} (1)^k*C(n, k)*C(2^(nk)1, n).
a(n) = (1/n!)*Sum_{k=0..n} Stirling1(n+1, k+1)*(2^k1)^n.
G.f.: Sum_{n>=0} log(1+(2^n1)*x)^n/((1+(2^n1)*x)*n!).  Paul D. Hanna and Vladeta Jovovic, Jan 16 2008


CROSSREFS

Main diagonal of A055154.
Cf. A048291, A088310, A181230, A259763.
Sequence in context: A297558 A283716 A202806 * A203323 A222683 A134474
Adjacent sequences: A054777 A054778 A054779 * A054781 A054782 A054783


KEYWORD

easy,nonn


AUTHOR

Vladeta Jovovic, May 21 2000


STATUS

approved



