A204618 a(n) = n^2 * B(n) where B(n) are the Bell numbers, A000110.
0, 1, 8, 45, 240, 1300, 7308, 42973, 264960, 1712907, 11597500, 82106970, 606757968, 4671909853, 37416267112, 311165672625, 2682916389632, 23947947373356, 220992885195516, 2105619936025577, 20689663294148800, 209417588925127191, 2181250417408504332
Offset: 0
Keywords
Links
- Muniru A Asiru, Table of n, a(n) for n = 0..550
Programs
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GAP
List([0..22],n->n^2*Bell(n)); # Muniru A Asiru, Apr 20 2019
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Mathematica
nn=20;a=Exp[Exp[x]-1];Range[0,nn]!CoefficientList[Series[x D[x D[a,x],x],{x,0,nn}],x] Table[n^2 BellB[n],{n,0,30}] (* Harvey P. Dale, Jul 01 2022 *)
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Python
from itertools import count, accumulate, islice def A204618_gen(): # generator of terms yield 0 blist, b = (1,), 1 for n in count(1): blist = list(accumulate(blist, initial=(b:=blist[-1]))) yield b*n**2 A204618_list = list(islice(A204618_gen(),20)) # Chai Wah Wu, Jun 22 2022
Formula
E.g.f.: (x+x^2+x^2 exp(x))exp(exp(x)+x-1) which is x*A'(x) where A(x) is the e.g.f. for A070071.