cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A204618 a(n) = n^2 * B(n) where B(n) are the Bell numbers, A000110.

Original entry on oeis.org

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

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Author

Geoffrey Critzer, Jan 17 2012

Keywords

Crossrefs

Programs

  • GAP
    List([0..22],n->n^2*Bell(n)); # Muniru A Asiru, Apr 20 2019
    
  • 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 *)
  • 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.

A306948 Expansion of e.g.f. (1 + x)*log(1 + x)*exp(x).

Original entry on oeis.org

0, 1, 3, 5, 8, 9, 19, -15, 216, -1407, 11803, -108483, 1106192, -12363703, 150381243, -1977666743, 27965386320, -423158076351, 6822782712723, -116781368777867, 2114916140765496, -40404117909336247, 812091479233464131, -17130720178674680031, 378423227774537955688
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 17 2019

Keywords

Crossrefs

Programs

  • Maple
    a:=series((1 + x)*log(1 + x)*exp(x),x=0,25): seq(n!*coeff(a, x, n), n=0..24); # Paolo P. Lava, Mar 26 2019
  • Mathematica
    nmax = 24; CoefficientList[Series[(1 + x) Log[1 + x] Exp[x], {x, 0, nmax}], x] Range[0, nmax]!
    Table[Sum[StirlingS1[n, k] BellB[k] k, {k, 0, n}], {n, 0, 24}]
    Table[Sum[(-1)^(k - 1) Binomial[n, k] (n - k + 1) (k - 1)!, {k, 1, n}], {n, 0, 24}]

Formula

a(n) = Sum_{k=0..n} Stirling1(n,k)*A000110(k)*k.
a(n) = Sum_{k=1..n} (-1)^(k-1)*binomial(n,k)*(n - k + 1)*(k - 1)!.
a(n) ~ exp(-1) * (-1)^n * n! / n^2. - Vaclav Kotesovec, Mar 18 2019
Conjecture: D-finite with recurrence a(n) +(n-5)*a(n-1) +(-3*n+10)*a(n-2) +3*(n-3)*a(n-3) +(-n+3)*a(n-4)=0. - R. J. Mathar, Aug 20 2021
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