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.

Previous Showing 21-27 of 27 results.

A375587 Expansion of e.g.f. 1 / (1 + x - x * exp(x^3/6)).

Original entry on oeis.org

1, 0, 0, 0, 4, 0, 0, 70, 1120, 0, 2800, 184800, 2217600, 200200, 39239200, 1513512000, 16166550400, 11435424000, 1029188160000, 31290941281600, 317363510464000, 821292151680000, 52198475641312000, 1387554839326656000, 14092570281613824000, 92349968764253200000
Offset: 0

Views

Author

Seiichi Manyama, Aug 19 2024

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1+x-x*exp(x^3/6))))
    
  • PARI
    a(n) = n!*sum(k=0, n\3, (n-3*k)!*stirling(k, n-3*k, 2)/(6^k*k!));

Formula

a(n) = n! * Sum_{k=0..floor(n/3)} (n-3*k)! * Stirling2(k,n-3*k)/(6^k*k!).

A375589 Expansion of e.g.f. 1 / (1 + x - x * exp(x^3)).

Original entry on oeis.org

1, 0, 0, 0, 24, 0, 0, 2520, 40320, 0, 604800, 39916800, 479001600, 259459200, 50854003200, 1961511552000, 21097146470400, 88921857024000, 8002967132160000, 243459152346009600, 2642401903325184000, 38318206628782080000, 2435557926202232832000
Offset: 0

Views

Author

Seiichi Manyama, Aug 19 2024

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1+x-x*exp(x^3))))
    
  • PARI
    a(n) = n!*sum(k=0, n\3, (n-3*k)!*stirling(k, n-3*k, 2)/k!);

Formula

a(n) = n! * Sum_{k=0..floor(n/3)} (n-3*k)! * Stirling2(k,n-3*k)/k!.

A367885 Expansion of e.g.f. 1/(1 - x * (exp(2*x) - 1)).

Original entry on oeis.org

1, 0, 4, 12, 128, 1040, 12672, 161728, 2481152, 41806080, 791613440, 16399944704, 371591995392, 9110211874816, 240670782291968, 6810264853463040, 205583847590985728, 6593508525460226048, 223913466256013918208, 8026367531323488993280
Offset: 0

Views

Author

Seiichi Manyama, Dec 04 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = n!*sum(k=0, n\2, 2^(n-k)*k!*stirling(n-k, k, 2)/(n-k)!);

Formula

a(0) = 1; a(n) = n * Sum_{k=2..n} 2^(k-1) * binomial(n-1,k-1) * a(n-k).
a(n) = n! * Sum_{k=0..floor(n/2)} 2^(n-k) * k! * Stirling2(n-k,k)/(n-k)!.

A367886 Expansion of e.g.f. 1/(1 - x * (exp(3*x) - 1)).

Original entry on oeis.org

1, 0, 6, 27, 324, 3645, 54918, 923643, 18061704, 394663833, 9607469130, 256997250279, 7502660832780, 237243300445125, 8079508278302958, 294800526215739315, 11473728720705019152, 474469344621574172721, 20774758472643152149650
Offset: 0

Views

Author

Seiichi Manyama, Dec 04 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = n!*sum(k=0, n\2, 3^(n-k)*k!*stirling(n-k, k, 2)/(n-k)!);

Formula

a(0) = 1; a(n) = n * Sum_{k=2..n} 3^(k-1) * binomial(n-1,k-1) * a(n-k).
a(n) = n! * Sum_{k=0..floor(n/2)} 3^(n-k) * k! * Stirling2(n-k,k)/(n-k)!.

A375683 Expansion of e.g.f. 1 / (1 + x * (exp(x) - 1)).

Original entry on oeis.org

1, 0, -2, -3, 20, 115, -306, -6307, -6616, 462663, 2956130, -38945951, -656504388, 2325876683, 145820995670, 562691968005, -33452317341616, -449954883966065, 7055017491780810, 233802046526955497, -571834988279277340, -112474674691684827501
Offset: 0

Views

Author

Seiichi Manyama, Aug 24 2024

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1+x*(exp(x)-1))))
    
  • PARI
    a(n) = n!*sum(k=0, n\2, (-1)^k*k!*stirling(n-k, k, 2)/(n-k)!);

Formula

a(0) = 1; a(n) = -n * Sum_{k=2..n} binomial(n-1,k-1) * a(n-k).
a(n) = n! * Sum_{k=0..floor(n/2)} (-1)^k * k! * Stirling2(n-k,k)/(n-k)!.

A220222 Triangular array read by rows. T(n,k) is the number of functional digraphs on {1,2,...,n} such that no node is at a distance greater than one from a cycle and there are k recurrent elements whose preimage contains only one element, n>=0, 0<=k<=n.

Original entry on oeis.org

1, 0, 1, 2, 0, 2, 3, 12, 0, 6, 28, 24, 72, 0, 24, 125, 400, 180, 480, 0, 120, 1146, 2220, 4680, 1440, 3600, 0, 720, 8827, 29064, 30870, 53760, 12600, 30240, 0, 5040, 94200, 272272, 545328, 409920, 638400, 120960, 282240, 0, 40320, 1007001, 3722688, 5989032, 9386496, 5518800, 7983360, 1270080, 2903040, 0, 362880
Offset: 0

Views

Author

Geoffrey Critzer, Dec 07 2012

Keywords

Comments

Row sums = A006153. Column for k=0 is A052848.

Examples

			1,
0,    1,
2,    0,    2,
3,    12,   0,    6,
28,   24,   72,   0,    24,
125,  400,  180,  480,  0,    120, 0
1146, 2220, 4680, 1440, 3600, 0,   720
		

Crossrefs

Cf. A006153.

Programs

  • Mathematica
    nn=6;a=x Exp[x];Range[0,nn]!CoefficientList[Series[1/(1-x (Exp[x]-1+y)),{x,0,nn}],{x,y}]//Grid

Formula

E.g.f.: 1/(1 - x*(exp(x) -1 + y)).

A355666 Square array T(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of e.g.f. 1/(1 - x^k/k! * (exp(x) - 1)).

Original entry on oeis.org

1, 1, 1, 1, 0, 3, 1, 0, 2, 13, 1, 0, 0, 3, 75, 1, 0, 0, 3, 28, 541, 1, 0, 0, 0, 6, 125, 4683, 1, 0, 0, 0, 4, 10, 1146, 47293, 1, 0, 0, 0, 0, 10, 195, 8827, 545835, 1, 0, 0, 0, 0, 5, 20, 1281, 94200, 7087261, 1, 0, 0, 0, 0, 0, 15, 35, 5908, 1007001, 102247563, 1, 0, 0, 0, 0, 0, 6, 35, 1176, 68076, 12814390, 1622632573
Offset: 0

Views

Author

Seiichi Manyama, Jul 13 2022

Keywords

Examples

			Square array begins:
     1,    1,   1,  1,  1, 1, 1, ...
     1,    0,   0,  0,  0, 0, 0, ...
     3,    2,   0,  0,  0, 0, 0, ...
    13,    3,   3,  0,  0, 0, 0, ...
    75,   28,   6,  4,  0, 0, 0, ...
   541,  125,  10, 10,  5, 0, 0, ...
  4683, 1146, 195, 20, 15, 6, 0, ...
		

Crossrefs

Columns k=0..3 give A000670, A052848, A353998, A353999.

Programs

  • PARI
    T(n, k) = n!*sum(j=0, n\(k+1), j!*stirling(n-k*j, j, 2)/(k!^j*(n-k*j)!));

Formula

T(0,k) = 1 and T(n,k) = binomial(n,k) * Sum_{j=k+1..n} binomial(n-k,j-k) * T(n-j,k) for n > 0.
T(n,k) = n! * Sum_{j=0..floor(n/(k+1))} j! * Stirling2(n-k*j,j)/(k!^j * (n-k*j)!).
Previous Showing 21-27 of 27 results.