A055127 - OEIS

%I #9 May 10 2013 12:44:29

%S 0,1,0,2,5,4,2,1,0,4,19,58,113,168,193,171,119,68,29,10,3,1,0,6,53,

%T 325,1551,6007,19533,54119,128936,266085,478223,751487,1035609,

%U 1254303,1336855,1254307,1035622,751526,478320,266272,129226,54484,19898,6297

%N Triangle T(n,k) of numbers of proper k-covers of an unlabeled n-set, k=1..2^n-2.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ProperCover.html">Proper covers</a>

%e [0, 1], [0, 2, 5, 4, 2, 1], [0, 4, 19, 58, 113, 168, 193, 171, 119, 68, 29, 10, 3, 1], ...; There are 113 proper 5-covers of an unlabeled 4-set.

%Y Cf. A052265, A055080, A007537. Row sums give A055152.

%K nonn,tabf

%O 2,4

%A _Vladeta Jovovic_, Jun 14 2000