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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A305991 Expansion of (1-27*x)^(1/9).

Original entry on oeis.org

1, -3, -36, -612, -11934, -250614, -5513508, -125235396, -2911722957, -68910776649, -1653858639576, -40143659706072, -983519662798764, -24285370135261788, -603664914790793016, -15091622869769825400, -379177024602966863175, -9568643738510163782475
Offset: 0

Views

Author

Seiichi Manyama, Jun 16 2018

Keywords

Crossrefs

(1-b*x)^(1/A003557(b)): A002420 (b=4), A004984 (b=8), A004990 (b=9), (-1)^n * A108735 (b=12), A301271 (b=16), (-1)^n * A108733 (b=18), A049393 (b=25), this sequence (b=27), A004996 (b=36), A303007 (b=240), A303055 (b=504), A305886 (b=1728).

Programs

  • PARI
    N=20; x='x+O('x^N); Vec((1-27*x)^(1/9))

Formula

a(n) = 3^n/n! * Product_{k=0..n-1} (9*k - 1) for n > 0.
a(n) ~ 27^n / (Gamma(-1/9) * n^(10/9)). - Vaclav Kotesovec, Jun 16 2018
D-finite with recurrence: n*a(n) +3*(-9*n+10)*a(n-1)=0. - R. J. Mathar, Jan 16 2020

A386416 G.f. A(x) satisfies A(x) = (1 + 9*x*A(x)^8)^(1/3).

Original entry on oeis.org

1, 3, 63, 1881, 65610, 2499336, 100777122, 4228144596, 182674383705, 8072369224920, 363154406671485, 16576444298006658, 765806677899249168, 35739548618003938440, 1682429522012566325460, 79793991407758199002740, 3809208342822290233767522, 182890356905449116974950200
Offset: 0

Views

Author

Seiichi Manyama, Jul 21 2025

Keywords

Crossrefs

Programs

  • Mathematica
    A386416[n_] := 9^n*Binomial[(8*n + 1)/3, n]/(8*n + 1);
    Array[A386416, 20, 0] (* Paolo Xausa, Aug 01 2025 *)
  • PARI
    apr(n, p, r) = r*binomial(n*p+r, n)/(n*p+r);
    a(n) = 9^n*apr(n, 8/3, 1/3);

Formula

a(n) = 9^n * binomial((8*n+1)/3,n)/(8*n+1).
G.f. A(x) satisfies A(x) = 1/A(-x*A(x)^13).
D-finite with recurrence 5*n*(n-1)*(n-2)*(5*n-8)*(5*n-11)*(5*n+1)*(5*n-2)*a(n) -3456*(8*n-11)*(8*n-5)*(4*n-1)*(8*n-23)*(2*n-5)*(8*n-17)*(4*n-7)*a(n-3)=0. - R. J. Mathar, Jul 30 2025

A380029 Expansion of e.g.f. (1 - 3*x*exp(x))^(1/3).

Original entry on oeis.org

1, -1, -4, -25, -252, -3545, -63806, -1397781, -36069272, -1071165745, -35977484250, -1348257912221, -55766033179220, -2523251585908521, -123972318738063446, -6572554273909419685, -373979858167243433136, -22731929051273411113313, -1470009560015441800798514
Offset: 0

Views

Author

Seiichi Manyama, Jan 09 2025

Keywords

Crossrefs

Programs

  • PARI
    a(n) = n!*sum(k=0, n, (-3)^k*k^(n-k)*binomial(1/3, k)/(n-k)!);

Formula

a(n) = n! * Sum_{k=0..n} (-3)^k * k^(n-k) * binomial(1/3,k)/(n-k)!.
Previous Showing 11-13 of 13 results.