A274392 - OEIS

%I #5 Jun 24 2016 22:52:44

%S 1,4,63,2056,112625,9266706,1067280319,163802295616,32300931452769,

%T 7956776354536450,2394142654816299431,863996246301971667600,

%U 368314015001746325448313,183100281424495288847092386,104989565698848905178879275775,68778360046311927838608116567296,51049027217135211093037275781929857,42614907995326324626989103964953188610,39750079580111447237206552931429888023399,41188867531604111691413161924808444678694800,47163303540183246052916530453746351377795346681

%N A diagonal of rectangular array A274390 of coefficients in the iterations of Euler's tree function (A000169).

%H Paul D. Hanna, <a href="/A274392/b274392.txt">Table of n, a(n) for n = 1..100</a>

%o (PARI) {ITERATE(F,n,k) = my(G=x +x*O(x^k)); for(i=1,n,G=subst(G,x,F));G}

%o {A274390(n,k) = my(TREE = serreverse(x*exp(-x +x*O(x^k)))); k!*polcoeff(ITERATE(TREE,n,k),k)}

%o /* Print A274390 */

%o for(n=0,10,for(k=1,10,print1(A274390(n,k),", "));print("..."))

%o /* Print this sequence, as a diagonal of A274390 */

%o for(n=1,20,print1(A274390(n,n),", "))

%Y Cf. A274390, A000169, A274389.

%K nonn

%O 1,2

%A _Paul D. Hanna_, Jun 24 2016