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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A094368 Triangle M(k,n) read by rows: coefficients of Meixner polynomials.

Original entry on oeis.org

1, 1, -1, 1, -5, 1, -14, 9, 1, -30, 89, 1, -55, 439, -225, 1, -91, 1519, -3429, 1, -140, 4214, -24940, 11025, 1, -204, 10038, -122156, 230481, 1, -285, 21378, -463490, 2250621, -893025, 1, -385, 41778, -1467290, 14466221, -23941125, 1, -506
Offset: 1

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Author

Ralf Stephan, Jun 03 2004

Keywords

Examples

			z,
z^2 - 1,
z^3 - 5*z,
z^4 - 14*z^2 + 9,
z^5 - 30*z^3 + 89*z,
z^6 - 55*z^4 + 439*z^2 - 225,
z^7 - 91*z^5 + 1519*z^3 - 3429*z,
z^8 - 140*z^6 + 4214*z^4 - 24940*z^2 + 11025,
z^9 - 204*z^7 + 10038*z^5 - 122156*z^3 + 230481*z,
		

Crossrefs

Essentially the same as A060338.
Cf. A060524.

Formula

Recurrence: M(0, z) = 1, M(1, z) = z, M(n+1, z) = z*M(n, z) - n^2*M(n-1, z).
G.f.: exp(z*arctan(x)) / sqrt(1+x^2).
The n-th (unsigned) row polynomial R(n, x) = (-i)^n * M(n, i*x) = n!*Sum_{k = 0..n} 2^k*binomial(n, k)*binomial(x/2 - 1/2, k). - Peter Bala, Mar 10 2024

A204420 Triangle T(n,k) giving number of degree-2n permutations which decompose into exactly k cycles of even length, k=0..n.

Original entry on oeis.org

1, 0, 1, 0, 6, 3, 0, 120, 90, 15, 0, 5040, 4620, 1260, 105, 0, 362880, 378000, 132300, 18900, 945, 0, 39916800, 45571680, 18711000, 3534300, 311850, 10395, 0, 6227020800, 7628100480, 3511347840, 794593800, 94594500, 5675670, 135135
Offset: 0

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Author

José H. Nieto S., Jan 15 2012

Keywords

Comments

The row polynomials t(n,x):= sum(T(n,k)*x^k, k=0..n) satisfy the recurrence relation t(n,x) = (2n-1)*(x+2n-2)*t(n-1,x), with t(0,x)=1, hence t(n,x)=(2n-1)!!*x(x+2)(x+4)...(x+2n-2).

Examples

			1;
0,        1,
0,        6,        3;
0,      120,       90,       15;
0,     5040,     4620,     1260,     105;
0,   362880,   378000,   132300,   18900,    945;
0, 39916800, 45571680, 18711000, 3534300, 311850, 10395;
		

Crossrefs

Row sums give: A001818. - Alois P. Heinz, Jul 21 2013

Programs

  • Maple
    T_row:= proc(n) local k; seq(doublefactorial(2*n-1)*2^(n-k)* coeff(expand(pochhammer(x, n)), x, k), k=0..n) end: seq(T_row(n), n=0..10);
  • Mathematica
    nn=12;Prepend[Map[Prepend[Select[#,#>0&],0]&,Table[(Range[0, nn]!CoefficientList[ Series[(1-x^2)^(-y/2),{x,0,nn}],{x,y}])[[n]],{n,3,nn,2}]],{1}]//Grid (* Geoffrey Critzer, Jul 21 2013 *)
  • PARI
    T(n,k) = (2*n)!/(2^n*n!)*(-2)^(n-k)*stirling(n,k,1); \\ Andrew Howroyd, Feb 12 2018

Formula

T(n,k) = (2n-1)!!*2^(n-k)*A132393(n,k).
T(n,k) = (2n-1)T(n-1,k-1) + (2n-1)(2n-2)*T(n-1,k); T(0,0)=1, T(n,0)=0 for n>0,
T(n,n) = (2n-1)!! = A001147(n).
T(n,1) = (2n-1)! = A009445(n-1).

A230696 Triangle read by rows related to double factorial of odd numbers (A001147).

Original entry on oeis.org

1, 0, 1, 1, 0, 2, 0, 11, 0, 4, 25, 0, 72, 0, 8, 0, 589, 0, 340, 0, 16, 2025, 0, 7010, 0, 1328, 0, 32, 0, 75319, 0, 55160, 0, 4592, 0, 64, 342225, 0, 1335328, 0, 334752, 0, 14592, 0, 128
Offset: 0

Views

Author

Philippe Deléham, Oct 27 2013

Keywords

Comments

The row polynomials t(n,x):= sum(T(n,k)*x^k, k=0..n) satisfy the recurrence relation t(n,x) = 2x*t(n-1,x) + ((2n-3)^2)*t(n-2,x); t(0,x) = 1, t(1,x) = x.

Examples

			Triangle begins:
1
0, 1
1, 0, 2
0, 11, 0, 4
25, 0, 72, 0, 8
0, 589, 0, 340, 0, 16
2025, 0, 7010, 0, 1328, 0, 32
0, 75319, 0, 55160, 0, 4592, 0, 64
		

Crossrefs

T(2n,0) = A007696(n)^2.
T(n,n) = A011782(n).
A001147 (row sums).
Cf. A060524 (similar sequence).

Formula

T(n,k) = 2*T(n-1,k-1) + ((2n-3)^2)*T(n-2,k); T(0,0) = 1, T(1,0) = 0, T(1,1) = 1, T(n,k) = 0 if k>n or if k<0.
Previous Showing 11-13 of 13 results.