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%I #9 Aug 18 2015 00:25:01
%S 0,1,4,18,88,470,2724,17010,113712,809262,6101820,48540778,405935688,
%T 3557404838,32577733972,310987560930,3087723669600,31823217868318,
%U 339845199259500,3754422961010522,42843681016834680,504339820818380694
%N Second column of PE^2.
%C Base matrix is in A011971; second power is in A078937; third power is in A078938; fourth power is in A078939.
%F PE=exp(matpascal(5))/exp(1); A = PE^2; a(n)=A[n,2] with exact integer arithmetic: PE=exp(matpascal(5)-matid(6)); A = PE^2; a(n)=A[n,2]
%p A056857 := proc(n,c) combinat[bell](n-1-c)*binomial(n-1,c) ; end: A078937 := proc(n,c) add( A056857(n,k)*A056857(k+1,c),k=0..n) ; end: A129323 := proc(n) A078937(n+1,1) ; end: seq(A129323(n),n=0..23) ; # _R. J. Mathar_, May 30 2008
%t Table[Sum[BellB[n, 2], {i, 0, n}], {n, -1, 20}] (* _Zerinvary Lajos_, Jul 16 2009 *)
%Y Cf. A056857, A078937, A078938, A078944, A078945, A000110.
%Y Cf. A078937, A078938, A129323, A129324, A129325, A027710.
%Y Cf. A129327, A129328, A129329, A078944, A129331, A129332, A129333.
%K nonn,easy
%O 0,3
%A _Gottfried Helms_, Apr 08 2007
%E More terms from _R. J. Mathar_, May 30 2008
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