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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A221176 a(n) = Sum_{i=0..n} Stirling2(n,i)*2^(4i).

Original entry on oeis.org

1, 16, 272, 4880, 91920, 1810192, 37142288, 791744272, 17490370320, 399558315792, 9421351690000, 228916588400400, 5723078052339472, 147025755978698512, 3876566243300318992, 104789417805394595600, 2901159958960121863952, 82188946843192555474704, 2380551266738846355103504, 70441182699006212824911632
Offset: 0

Views

Author

N. J. A. Sloane, Jan 04 2013

Keywords

Comments

The number of ways of putting n labeled balls into a set of bags and then putting the bags into 16 labeled boxes. - Peter Bala, Mar 23 2013

Crossrefs

Programs

  • Mathematica
    With[{nn=20},CoefficientList[Series[Exp[16 (Exp[x]-1)],{x,0,nn}],x] Range[0,nn]!] (* Harvey P. Dale, Dec 19 2024 *)

Formula

E.g.f. exp(16*(exp(x) - 1)). - Peter Bala, Mar 23 2013

A345077 a(0) = 1; a(n) = 6 * Sum_{k=1..n} binomial(n,k) * a(k-1).

Original entry on oeis.org

1, 6, 48, 414, 3876, 38946, 416808, 4722774, 56379756, 706236426, 9250945008, 126342991614, 1794459834036, 26445918969906, 403610795535288, 6367606516836774, 103683034842399996, 1739933892930544986, 30052751213767045248, 533635421576480845134, 9730601644306627161156
Offset: 0

Views

Author

Ilya Gutkovskiy, Jun 07 2021

Keywords

Crossrefs

Programs

  • Mathematica
    a[0] = 1; a[n_] := a[n] = 6 Sum[Binomial[n, k] a[k - 1], {k, 1, n}]; Table[a[n], {n, 0, 20}]
    nmax = 20; A[] = 0; Do[A[x] = 1 + 6 x A[x/(1 - x)]/(1 - x)^2 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]

Formula

G.f. A(x) satisfies: A(x) = 1 + 6 * x * A(x/(1 - x)) / (1 - x)^2.

A299824 a(n) = (1/e^n)*Sum_{j >= 1} j^n * n^j / (j-1)!.

Original entry on oeis.org

2, 22, 309, 5428, 115155, 2869242, 82187658, 2661876168, 96202473183, 3838516103310, 167606767714397, 7949901069639228, 407048805012563038, 22376916254447538882, 1314573505901491675965, 82188946843192555474704, 5448870914168179374456623, 381819805747937892412056342
Offset: 1

Views

Author

Pedro Caceres, Feb 19 2018

Keywords

Comments

For m>1, A242817(m) and a(m-1) are also the m-th and (m+1)-st terms of the sequences "Number of ways of placing X labeled balls into X unlabeled (but (m-1)-colored) boxes". For instance, sequence A144180 for 5-colored boxes (m = 6), has A144180(6) = 12880, and A144180(7) = 115155, which are A242817(6) and a(5) respectively. Same pattern can be observed for A027710, A144223, A144263 (comment added after Omar E. Pol's formula).

Examples

			a(4) = (1/e^4)*Sum_{j >= 1} j^4 * 4^j / (j-1)! = 5428.
		

Crossrefs

Programs

  • PARI
    a(n) = round(exp(-n)*suminf(j = 1, (j^n)*(n^j)/(j-1)!)); \\ Michel Marcus, Feb 24 2018
    
  • PARI
    A299824(n,f=exp(n),S=n/f,t)=for(j=2,oo,S+=(t=j^n*n^j)/(f*=j-1);tn&&return(ceil(S))) \\ For n > 23, use \p## with some ## >= 2n. - M. F. Hasler, Mar 09 2018

Formula

a(n) = A189233(n+1,n). - Omar E. Pol, Feb 24 2018
a(n) ~ exp(n/LambertW(1) - 2*n) * n^(n + 1) / (sqrt(1 + LambertW(1)) * LambertW(1)^(n + 1)). - Vaclav Kotesovec, Mar 08 2018
Or: a(n) ~ (1/sqrt(1+w)) * exp(1/w-2)^n * (n/w)^(n+1), with w = LambertW(1) ~ 0.56714329... The relative error decreases from 10^-2 for a(2) to 10^-3 for a(15), but reaches 10^-3.5 only at a(45). - M. F. Hasler, Mar 09 2018

A276506 E.g.f.: exp(9*(exp(x)-1)).

Original entry on oeis.org

1, 9, 90, 981, 11511, 144108, 1911771, 26730981, 392209380, 6016681467, 96202473183, 1599000785730, 27563715220509, 491777630207037, 9064781481234546, 172346601006842337, 3375007346801025099, 67983454804021156548, 1406921223577401454239, 29881379179971835132761
Offset: 0

Views

Author

Vincenzo Librandi, Sep 17 2016

Keywords

Comments

Number of ways of placing n labeled balls into n unlabeled (but 9-colored) boxes.

Crossrefs

Cf. similar sequences with e.g.f. exp(k*(exp(x)-1)): A001861 (k=2), A027710 (k=3), A078944 (k=4), A144180 (k=5) A144223 (k=6), A144263 (k=7), A221159 (k=8), this sequence (k=9), A276507 (k=10).

Programs

  • Maple
    a:= proc(n) option remember; `if`(n=0, 1,
          (1+add(binomial(n-1, k-1)*a(n-k), k=1..n-1))*9)
        end:
    seq(a(n), n=0..25);  # Alois P. Heinz, Sep 25 2017
  • Mathematica
    Table[BellB[n, 9], {n, 0, 30}]
  • PARI
    my(x='x+O('x^99)); Vec(serlaplace(exp(9*(exp(x)-1)))) \\ Altug Alkan, Sep 17 2016

Formula

G.f.: A(x) satisfies 9*(x/(1-x))*A(x/(1-x)) = A(x)-1; nine times the binomial transform equals this sequence shifted one place left.
Previous Showing 11-14 of 14 results.