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 1-5 of 5 results.

A362300 a(n) = n! * Sum_{k=0..floor(n/3)} (n/3)^k * binomial(n-2*k,k)/(n-2*k)!.

Original entry on oeis.org

1, 1, 1, 7, 33, 101, 1681, 14211, 72577, 1906633, 23242401, 166218911, 5966236321, 95016917997, 873707885233, 39767572858651, 781865428682241, 8787169718273681, 484500265577706817, 11335266937098816183, 150554918241183405601, 9749671976020428623221
Offset: 0

Views

Author

Seiichi Manyama, Apr 15 2023

Keywords

Comments

Let k be a positive integer. It appears that reducing this sequence modulo k produces an eventually periodic sequence with period a multiple of k. For example, modulo 9 the sequence becomes [1, 1, 1, 7, 6, 2, 7, 0, 1, 1, 0, 8, 7, 0, 7, 7, 0, 8, 1, 0, 1, 7, 0, 2, 7, 0, 1, 1, 0, 8, 7, 0, 7, 7, 0, 8, 1, 0, 1, 7, 0, 2, 7, 0, 1, ...], with an apparent period [2, 7, 0, 1, 1, 0, 8, 7, 0, 7, 7, 0, 8, 1, 0, 1, 7, 0] of length 18 starting at a(5). - Peter Bala, Apr 16 2023

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp((-lambertw(-x^3))^(1/3))/(1+lambertw(-x^3))))

Formula

a(n) = A362043(n,2*n).
a(n) = n! * [x^n] exp(x + n*x^3/3).
E.g.f.: exp( ( -LambertW(-x^3) )^(1/3) ) / (1 + LambertW(-x^3)).
a(n) ~ (1 + 2*cos(2*Pi*mod(n,3)/3 - sqrt(3)/2)/exp(3/2)) * n^n / (sqrt(3) * exp(2*n/3 - 1)). - Vaclav Kotesovec, Apr 18 2023

A362302 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = n! * Sum_{j=0..floor(n/3)} (-k/6)^j * binomial(n-2*j,j)/(n-2*j)!.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, -1, -3, 1, 1, 1, 1, -2, -7, -9, 1, 1, 1, 1, -3, -11, -19, -9, 1, 1, 1, 1, -4, -15, -29, 1, 36, 1, 1, 1, 1, -5, -19, -39, 31, 211, 225, 1, 1, 1, 1, -6, -23, -49, 81, 526, 1009, 477, 1, 1, 1, 1, -7, -27, -59, 151, 981, 2353, 953, -819, 1
Offset: 0

Views

Author

Seiichi Manyama, Apr 15 2023

Keywords

Examples

			Square array begins:
  1,  1,   1,   1,   1,   1,   1, ...
  1,  1,   1,   1,   1,   1,   1, ...
  1,  1,   1,   1,   1,   1,   1, ...
  1,  0,  -1,  -2,  -3,  -4,  -5, ...
  1, -3,  -7, -11, -15, -19, -23, ...
  1, -9, -19, -29, -39, -49, -59, ...
  1, -9,   1,  31,  81, 151, 241, ...
		

Crossrefs

Columns k=0..2 give A000012, A351929, A362309.
Main diagonal gives A362303.
T(n,2*n) gives A362304.
T(n,6*n) gives A362305.

Programs

  • PARI
    T(n, k) = n!*sum(j=0, n\3, (-k/6)^j/(j!*(n-3*j)!));

Formula

E.g.f. of column k: exp(x - k*x^3/6).
T(n,k) = T(n-1,k) - k * binomial(n-1,2) * T(n-3,k) for n > 2.
T(n,k) = n! * Sum_{j=0..floor(n/3)} (-k/6)^j / (j! * (n-3*j)!).

A362378 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = n! * Sum_{j=0..floor(n/3)} (k/6)^j * (j+1)^(n-2*j-1) / (j! * (n-3*j)!).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 3, 9, 1, 1, 1, 1, 4, 17, 41, 1, 1, 1, 1, 5, 25, 81, 191, 1, 1, 1, 1, 6, 33, 121, 441, 1191, 1, 1, 1, 1, 7, 41, 161, 751, 3641, 9353, 1, 1, 1, 1, 8, 49, 201, 1121, 7351, 33825, 77897, 1
Offset: 0

Views

Author

Seiichi Manyama, Apr 20 2023

Keywords

Examples

			Square array begins:
  1,   1,   1,   1,    1,    1,    1, ...
  1,   1,   1,   1,    1,    1,    1, ...
  1,   1,   1,   1,    1,    1,    1, ...
  1,   2,   3,   4,    5,    6,    7, ...
  1,   9,  17,  25,   33,   41,   49, ...
  1,  41,  81, 121,  161,  201,  241, ...
  1, 191, 441, 751, 1121, 1551, 2041, ...
		

Crossrefs

Columns k=0..3 give A000012, A362381, A362390, A362391.

Programs

  • PARI
    T(n, k) = n! * sum(j=0, n\3, (k/6)^j*(j+1)^(n-2*j-1)/(j!*(n-3*j)!));

Formula

E.g.f. A_k(x) of column k satisfies A_k(x) = exp(x + k*x^3/6 * A_k(x)).
A_k(x) = exp(x - LambertW(-k*x^3/6 * exp(x))).
A_k(x) = -6 * LambertW(-k*x^3/6 * exp(x))/(k*x^3) for k > 0.

A362301 a(n) = n! * Sum_{k=0..floor(n/3)} n^k * binomial(n-2*k,k)/(n-2*k)!.

Original entry on oeis.org

1, 1, 1, 19, 97, 301, 13681, 124951, 647809, 46543897, 612367201, 4447574011, 436897375201, 7505523945349, 70104150466897, 8735878156045951, 185209511009456641, 2114594302777738801, 319284313084581674689, 8053189772356178472547
Offset: 0

Views

Author

Seiichi Manyama, Apr 15 2023

Keywords

Crossrefs

Cf. A362043.

Programs

  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(exp((-lambertw(-3*x^3)/3)^(1/3))/(1+lambertw(-3*x^3))))

Formula

a(n) = A362043(n,6*n).
a(n) = n! * [x^n] exp(x + n*x^3).
E.g.f.: exp( ( -LambertW(-3*x^3)/3 )^(1/3) ) / (1 + LambertW(-3*x^3)).
a(n) ~ (1 + 2*cos(2*Pi*mod(n,3)/3 - 3^(1/6)/2)*exp(-3^(2/3)/2)) * 3^(n/3 - 1/2) * n^n / exp(2*n/3 - 1/3^(1/3)). - Vaclav Kotesovec, Apr 18 2023

A362173 a(n) = n! * Sum_{k=0..floor(n/3)} (n/6)^k * binomial(n-2*k,k)/(n-2*k)!.

Original entry on oeis.org

1, 1, 1, 4, 17, 51, 481, 3676, 18369, 272917, 3011201, 21058236, 427112401, 6160655359, 55380250017, 1423658493076, 25361574327041, 278603741558601, 8673295084155649, 183914415577719892, 2387417408385462801, 87273239189497636171, 2146479566819857007201
Offset: 0

Views

Author

Seiichi Manyama, Apr 14 2023

Keywords

Crossrefs

Main diagonal of A362043.

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp((-2*lambertw(-x^3/2))^(1/3))/(1+lambertw(-x^3/2))))

Formula

a(n) = n! * [x^n] exp(x + n*x^3/6).
E.g.f.: exp( ( -2*LambertW(-x^3/2) )^(1/3) ) / (1 + LambertW(-x^3/2)).
Showing 1-5 of 5 results.