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Search: id:A094574
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A094574 Number of (<=2)-covers of an n-set. +0
3
1, 1, 5, 40, 457, 6995, 136771, 3299218, 95668354, 3268445951, 129468914524, 5868774803537, 301122189141524, 17327463910351045, 1109375488487304027, 78484513540137938209, 6098627708074641312182, 517736625823888411991202 (list; graph; listen)
OFFSET

0,3

FORMULA

Row sums of A094573. E.g.f: exp(-1-1/2*(exp(x)-1))*Sum(exp(x*binomial(n+1, 2))/n!, n=0..infinity) or exp((1-exp(x))/2)*Sum(A094577 (n)*(x/2)^n/n!, n=0..infinity).

CROSSREFS

Cf. A002718, A020554.

Sequence in context: A000359 A121886 A052868 this_sequence A090362 A088695 A113079

Adjacent sequences: A094571 A094572 A094573 this_sequence A094575 A094576 A094577

KEYWORD

nonn

AUTHOR

Goran Kilibarda, Vladeta Jovovic (vladeta(AT)Eunet.yu), May 12 2004

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Last modified July 23 17:35 EDT 2008. Contains 142285 sequences.


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