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.

Showing 1-3 of 3 results.

A294042 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f.: exp((1+x)^k - 1).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 3, 6, 1, 0, 1, 4, 15, 20, 1, 0, 1, 5, 28, 87, 76, 1, 0, 1, 6, 45, 232, 585, 312, 1, 0, 1, 7, 66, 485, 2248, 4383, 1384, 1, 0, 1, 8, 91, 876, 6145, 24544, 35919, 6512, 1, 0, 1, 9, 120, 1435, 13716, 88245, 295456, 318195, 32400, 1, 0
Offset: 0

Views

Author

Seiichi Manyama, Oct 22 2017

Keywords

Examples

			Square array A(n,k) begins:
   1, 1,   1,    1,     1,     1, ...
   0, 1,   2,    3,     4,     5, ...
   0, 1,   6,   15,    28,    45, ...
   0, 1,  20,   87,   232,   485, ...
   0, 1,  76,  585,  2248,  6145, ...
   0, 1, 312, 4383, 24544, 88245, ...
		

Crossrefs

Columns k=0..5 give A000007, A000012, A000898, A192989, A202824, A202825.
Rows n=0..2 give A000012, A001477, A000384.
Main diagonal gives A294045.

Formula

A(0,k) = 1 and A(n,k) = k * (n-1)! * Sum_{j=1..min(k,n)} binomial(k-1,j-1) * A(n-j,k)/(n-j)! for n > 0.
A(n,k) = Sum_{j=0..n} k^j * Stirling1(n,j) * Bell(j). - Seiichi Manyama, Jan 31 2024

A202824 Expansion of e.g.f.: exp( (1+x)^4 - 1 ).

Original entry on oeis.org

1, 4, 28, 232, 2248, 24544, 295456, 3869632, 54555328, 821239552, 13115934976, 221076780544, 3915685846528, 72609585620992, 1405168845395968, 28302270409560064, 591874919018500096, 12824294700196052992, 287350628454224478208, 6647086535396002004992
Offset: 0

Views

Author

Paul D. Hanna, Dec 25 2011

Keywords

Examples

			E.g.f.: A(x) = 1 + 4*x + 28*x^2/2! + 232*x^3/3! + 2248*x^4/4! +...
where A(x) = exp(4*x + 6*x^2 + 4*x^3 + x^4).
		

Crossrefs

Programs

  • GAP
    List([0..20], n-> Sum([0..n], k-> (-1)^(n-k)*4^k*Bell(k)* Stirling1(n,k) )); # G. C. Greubel, Jul 25 2019
  • Magma
    [(&+[4^k*Bell(k)*StirlingFirst(n,k): k in [0..n]]): n in [0..20]]; // G. C. Greubel, Jul 25 2019
    
  • Mathematica
    CoefficientList[Series[Exp[(1+x)^4-1], {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, May 23 2013 *)
    Table[Sum[ (-1)^(n - k) Abs[StirlingS1[n, k]] 4^k BellB[k], {k, 0, n}], {n, 0, 100}] (* Emanuele Munarini, Aug 31 2017 *)
  • Maxima
    a(n) := sum((-1)^(n-k)*abs(stirling1(n,k))*4^k*belln(k),k,0,n);
    makelist(a(n),n,0,12); /* Emanuele Munarini, Aug 31 2017 */
    
  • PARI
    {a(n)=n!*polcoeff(exp((1+x +x*O(x^n))^4-1),n)}
    
  • PARI
    {Stirling1(n, k)=n!*polcoeff(binomial(x, n), k)}
    {Bell(n)=n!*polcoeff(exp(exp(x+x*O(x^n))-1), n)}
    {a(n)=sum(k=0, n, Stirling1(n, k)*Bell(k) * 4^k)}
    
  • Sage
    [sum((-1)^(n-k)*4^k*bell_number(k)*stirling_number1(n,k) for k in (0..n)) for n in (0..20)] # G. C. Greubel, Jul 25 2019
    

Formula

a(n) = Sum_{k=0..n} Stirling1(n, k)*Bell(k) * 4^k.
a(n) ~ n^(3*n/4)*2^(n/2-1)*exp(-3/4+5/16*sqrt(2)*n^(1/4)+sqrt(2)*n^(3/4)-3/4*n+3/4*sqrt(n)). - Vaclav Kotesovec, May 23 2013
a(n+4) - 4*a(n+3) - 12*(n+3)*a(n+2) - 12*(n+2)*(n+3)*a(n+1) - 4*(n+1)*(n+2)*(n+3)*a(n) = 0. - Emanuele Munarini, Aug 31 2017

A369753 Expansion of e.g.f. exp(1 - (1+x)^5).

Original entry on oeis.org

1, -5, 5, 115, -95, -8245, -21275, 896275, 8801825, -95466725, -2703832475, -3522650125, 717727962625, 9961465952875, -118944021914875, -5634631318806125, -37511809003469375, 2020875725751906875, 55489065505990733125, -65182838564153418125
Offset: 0

Views

Author

Seiichi Manyama, Jan 30 2024

Keywords

Crossrefs

Column k=5 of A369738.

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(1-(1+x)^5)))

Formula

a(0) = 1; a(n) = -5 * (n-1)! * Sum_{k=1..min(5,n)} binomial(4,k-1) * a(n-k)/(n-k)!.
a(n) = Sum_{k=0..n} 5^k * Stirling1(n,k) * A000587(k).
Showing 1-3 of 3 results.