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 1-6 of 6 results.

A289147 Number of (n+1) X (n+1) binary matrices M with at most one 1 in each of the first n rows and each of the first n columns and M[n+1,n+1] = 0.

Original entry on oeis.org

1, 5, 34, 286, 2840, 32344, 414160, 5876336, 91356544, 1542401920, 28075364096, 547643910400, 11389266525184, 251428006132736, 5869482147358720, 144413021660821504, 3733822274973040640, 101181690628832198656, 2867011297057247002624, 84764595415605494743040
Offset: 0

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Author

Alois P. Heinz, Jun 26 2017

Keywords

Comments

Number of marriage patterns between a labeled set X of n women and a labeled set Y of n men (all heterosexual): some couples can be formed where one partner is from X and the other from Y, some members of X and Y marry external (unlabeled) partners, and some do not marry.

Examples

			a(1) = 5:
[0 0]  [1 0]  [0 1]  [0 0]  [0 1]
[0 0]  [0 0]  [0 0]  [1 0]  [1 0] .
.
a(2) = 34:
[0 0 0]  [0 0 0]  [0 0 0]  [0 0 0]  [0 0 0]  [0 0 0]  [0 0 0]
[0 0 0]  [0 0 0]  [0 0 0]  [0 0 0]  [0 0 1]  [0 0 1]  [0 0 1]
[0 0 0]  [0 1 0]  [1 0 0]  [1 1 0]  [0 0 0]  [0 1 0]  [1 0 0]
.
[0 0 0]  [0 0 0]  [0 0 0]  [0 0 0]  [0 0 0]  [0 0 1]  [0 0 1]
[0 0 1]  [0 1 0]  [0 1 0]  [1 0 0]  [1 0 0]  [0 0 0]  [0 0 0]
[1 1 0]  [0 0 0]  [1 0 0]  [0 0 0]  [0 1 0]  [0 0 0]  [0 1 0]
.
[0 0 1]  [0 0 1]  [0 0 1]  [0 0 1]  [0 0 1]  [0 0 1]  [0 0 1]
[0 0 0]  [0 0 0]  [0 0 1]  [0 0 1]  [0 0 1]  [0 0 1]  [0 1 0]
[1 0 0]  [1 1 0]  [0 0 0]  [0 1 0]  [1 0 0]  [1 1 0]  [0 0 0]
.
[0 0 1]  [0 0 1]  [0 0 1]  [0 1 0]  [0 1 0]  [0 1 0]  [0 1 0]
[0 1 0]  [1 0 0]  [1 0 0]  [0 0 0]  [0 0 0]  [0 0 1]  [0 0 1]
[1 0 0]  [0 0 0]  [0 1 0]  [0 0 0]  [1 0 0]  [0 0 0]  [1 0 0]
.
[0 1 0]  [1 0 0]  [1 0 0]  [1 0 0]  [1 0 0]  [1 0 0]
[1 0 0]  [0 0 0]  [0 0 0]  [0 0 1]  [0 0 1]  [0 1 0]
[0 0 0]  [0 0 0]  [0 1 0]  [0 0 0]  [0 1 0]  [0 0 0]  .
		

Crossrefs

Programs

  • Maple
    a:= proc(n) option remember; `if`(n<2, 4*n+1,
          (2*n+3)*a(n-1)-(n-1)^2*a(n-2))
        end:
    seq(a(n), n=0..25);
    # second Maple program:
    a:= n-> n-> n! * add(binomial(n, i)*4^i/i!, i=0..n):
    seq(a(n), n=0..25);
    # third Maple program:
    a:= n-> n!* simplify(LaguerreL(n, -4), 'LaguerreL'):
    seq(a(n), n=0..25);
  • Mathematica
    Table[n! LaguerreL[n, -4], {n, 0, 30}] (* Indranil Ghosh, Jul 06 2017 *)
  • Python
    from mpmath import *
    mp.dps=150
    l=chop(taylor(lambda x:exp(4*x/(1-x))/(1-x), 0, 31))
    print([int(fac(i)*l[i]) for i in range(len(l))]) # Indranil Ghosh, Jul 06 2017
    # or #
    from mpmath import *
    mp.dps=100
    def a(n): return int(fac(n)*laguerre(n, 0, -4))
    print([a(n) for n in range(31)]) # Indranil Ghosh, Jul 06 2017

Formula

E.g.f.: exp(4*x/(1-x))/(1-x).
a(n) = Sum_{i=0..n} i! * (2^(n-i)*binomial(n,i))^2.
a(n) = Sum_{i=0..n} (n-i)! * 4^i * binomial(n,i)^2.
a(n) = n! * Sum_{i=0..n} 4^i/i! * binomial(n,i).
a(n) = (2*n+3)*a(n-1)-(n-1)^2*a(n-2) for n>=2, a(n) = 4*n+1 for n<2.
a(n) = n! * Laguerre(n,-4) = n! * A160611(n)/A160612(n).
a(n) ~ exp(-2 + 4*sqrt(n) - n) * n^(n + 1/4) / 2 * (1 + 163/(96*sqrt(n))). - Vaclav Kotesovec, Nov 13 2017
Sum_{n>=0} a(n) * x^n / (n!)^2 = exp(x) * Sum_{n>=0} 4^n * x^n / (n!)^2. - Ilya Gutkovskiy, Jul 17 2020

A341014 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals, where T(n,k) = Sum_{j=0..n} k^j * j! * binomial(n,j)^2.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 7, 1, 1, 4, 17, 34, 1, 1, 5, 31, 139, 209, 1, 1, 6, 49, 352, 1473, 1546, 1, 1, 7, 71, 709, 5233, 19091, 13327, 1, 1, 8, 97, 1246, 13505, 95836, 291793, 130922, 1, 1, 9, 127, 1999, 28881, 318181, 2080999, 5129307, 1441729, 1
Offset: 0

Views

Author

Seiichi Manyama, Feb 02 2021

Keywords

Examples

			Square array begins:
  1,    1,     1,     1,      1,      1, ...
  1,    2,     3,     4,      5,      6, ...
  1,    7,    17,    31,     49,     71, ...
  1,   34,   139,   352,    709,   1246, ...
  1,  209,  1473,  5233,  13505,  28881, ...
  1, 1546, 19091, 95836, 318181, 830126, ...
		

Crossrefs

Columns 0..4 give A000012, A002720, A025167, A102757, A102773.
Rows 0..2 give A000012, A000027(n+1), A056220(n+1).
Main diagonal gives A330260.
Cf. A307883.

Programs

  • Mathematica
    T[n_, k_] := Sum[If[j == k == 0, 1, k^j]*j!*Binomial[n, j]^2, {j, 0, n}]; Table[T[k, n - k], {n, 0, 9}, {k, 0, n}] // Flatten (* Amiram Eldar, Feb 02 2021 *)
  • PARI
    {T(n,k) = sum(j=0, n, k^j*j!*binomial(n, j)^2)}

Formula

E.g.f. of column k: exp(x/(1-k*x)) / (1-k*x).
T(n,k) = (2*k*n-k+1) * T(n-1,k) - k^2 * (n-1)^2 * T(n-2,k) for n > 1.

A330260 a(n) = n! * Sum_{k=0..n} binomial(n,k) * n^(n - k) / k!.

Original entry on oeis.org

1, 2, 17, 352, 13505, 830126, 74717857, 9263893892, 1513712421377, 315230799073690, 81499084718806001, 25612081645835777192, 9615370149488574778177, 4250194195208050117007942, 2184834047906975645398282625, 1292386053018890618812398220876
Offset: 0

Views

Author

Ilya Gutkovskiy, Dec 18 2019

Keywords

Crossrefs

Programs

  • Magma
    [Factorial(n)*&+[Binomial(n,k)*n^(n-k)/Factorial(k):k in [0..n]]:n in [0..15]]; // Marius A. Burtea, Dec 18 2019
  • Mathematica
    Join[{1}, Table[n! Sum[Binomial[n, k] n^(n - k)/k!, {k, 0, n}], {n, 1, 15}]]
    Join[{1}, Table[n^n n! LaguerreL[n, -1/n], {n, 1, 15}]]
    Table[n! SeriesCoefficient[Exp[x/(1 - n x)]/(1 - n x), {x, 0, n}], {n, 0, 15}]
  • PARI
    a(n) = n! * sum(k=0, n, binomial(n,k) * n^(n-k)/k!); \\ Michel Marcus, Dec 18 2019
    

Formula

a(n) = n! * [x^n] exp(x/(1 - n*x)) / (1 - n*x).
a(n) = Sum_{k=0..n} binomial(n,k)^2 * n^k * k!.
a(n) ~ sqrt(2*Pi) * BesselI(0,2) * n^(2*n + 1/2) / exp(n). - Vaclav Kotesovec, Dec 18 2019

A102757 a(n) = Sum_{i=0..n} C(n,i)^2 * i! * 3^i.

Original entry on oeis.org

1, 4, 31, 352, 5233, 95836, 2080999, 52189096, 1482977857, 47053929268, 1648037039791, 63125834205424, 2624096058047281, 117620219281363852, 5653607876781921463, 290035426344483253816, 15814774125898034896129
Offset: 0

Views

Author

Miklos Kristof, Mar 16 2005

Keywords

Comments

Primes in this sequence include: a(2)=31, a(4)=5233. Semiprimes in this sequence include: a(1) = 2^2, a(6) = 31 * 67129, a(8) = 127 * 11676991. - Jonathan Vos Post, Mar 17 2005

Crossrefs

Programs

  • Maple
    seq(sum('binomial(k,i)^2*i!*3^i', 'i'=0..k),k=0..30);
  • Mathematica
    f[n_] := Sum[k!*3^k*Binomial[n, k]^2, {k, 0, n}]; Table[ f[n], {n, 0, 16}] (* or *)
    Range[0, 16]! CoefficientList[ Series[1/(1 - 3x)*Exp[x/(1 - 3x)], {x, 0, 16}], x] (* Robert G. Wilson v, Mar 16 2005 *)

Formula

E.g.f.: 1/(1-3x)*exp(x/(1-3x)).
E.g.f.: exp(3*x) * Sum_{n>=0} x^n/n!^2 = Sum_{n>=0} a(n)*x^n/n!^2. [Paul D. Hanna, Nov 18 2011]
a(n) = 2*(3*n-1)*a(n-1) - 9*(n-1)^2*a(n-2). - Vaclav Kotesovec, Sep 29 2013
a(n) ~ (3*n)^(n+1/4)*exp(2*sqrt(n/3)-n-1/6)/sqrt(2) * (1 + 103/(144*sqrt(3*n))). - Vaclav Kotesovec, Sep 29 2013

Extensions

More terms from Robert G. Wilson v, Mar 16 2005

A121079 a(n) = Sum_{i=0..n} C(n,i)^2*i!*4^i + 2^n*n!.

Original entry on oeis.org

2, 7, 57, 757, 13889, 322021, 8962225, 289928549, 10666353409, 439225736005, 19999574572721, 997265831223685, 54028099173536449, 3159178743189436709, 198259676112757095985, 13289233274778582230821, 947420482287986880154625, 71574264415491967142194309
Offset: 0

Views

Author

N. J. A. Sloane, Aug 11 2006

Keywords

Crossrefs

Programs

  • Mathematica
    Array[Sum[Binomial[#, i]^2*i!*4^i, {i, 0, #}] + 2^#*#! &, 18, 0] (* Michael De Vlieger, Nov 28 2018 *)
  • PARI
    a(n) = 2^n*n! + sum(i=0, n, binomial(n,i)^2*i!*4^i); \\ Michel Marcus, May 31 2018

A121080 a(n) = Sum_{i=0..n} C(n,i)^2*i!*4^i + (1-2^n)*2^(n-1)*n!.

Original entry on oeis.org

1, 4, 37, 541, 10625, 258661, 7464625, 248318309, 9339986689, 391569431365, 18095180332721, 913513359466885, 50008961524486849, 2950209091316054309, 186558089772409191985, 12587159519294553302821, 902488447534988078746625, 68518909362619336345906309
Offset: 0

Views

Author

N. J. A. Sloane, Aug 11 2006

Keywords

Crossrefs

Programs

  • Mathematica
    Array[Sum[Binomial[#, i]^2*i!*4^i, {i, 0, #}] + (1 - 2^#)*2^(# - 1)*#! &, 18, 0] (* Michael De Vlieger, Nov 28 2018 *)
  • PARI
    a(n) = (1-2^n)*2^(n-1)*n! + sum(i=0, n, binomial(n,i)^2*i!*4^i); \\ Michel Marcus, May 31 2018
Showing 1-6 of 6 results.