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%I #11 Oct 17 2017 14:34:38
%S 1,4,40,612,11976,276836,7336248,219610532,7331824360,269576919908,
%T 10796426089880,466904884431268,21658080409800264,1071807203930733668,
%U 56328256034260866296,3131089417758323092388
%N E.g.f. exp(sum_{d|M} (exp(d*x)-1)/d), M=15.
%H Vincenzo Librandi, <a href="/A141011/b141011.txt">Table of n, a(n) for n = 0..200</a>
%t u[0, j_]: = 1; u[k_, j_]: = u[k, j] = Sum[Binomial[k-1, i-1]Plus@@(u[k-i, j]#^(i-1)&/@Divisors[j]), {i, k}]; Table[u[n, 15], {n, 0, 30}] (* _Vincenzo Librandi_, Dec 12 2012 *)
%Y Column k=15 of A162663.
%K nonn
%O 0,2
%A _R. J. Mathar_, Jul 11 2008
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