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.

A103353 First column of triangular matrix A103244.

Original entry on oeis.org

1, 2, 20, 512, 25392, 2093472, 260555392, 45819233280, 10849051434240, 3334632688448000, 1292876470540099584, 617862114722159788032, 357118557050589336432640, 245715466325821945360588800, 198568949299946066906578944000, 186309450278791634742517692366848
Offset: 1

Views

Author

Paul D. Hanna, Feb 02 2005

Keywords

Crossrefs

Cf. A103244.

Programs

  • Mathematica
    nmax = 16;
    P = Table[If[n >= k, (-k^2-k)^(n-k)/(n-k)!, 0], {n, 1, nmax}, {k, 1, nmax}] // Inverse;
    T[n_, k_] := If[n < k || k < 1, 0, P[[n, k]] (n - k)!];
    a[n_] := T[n, 1];
    Array[a, nmax] (* Jean-François Alcover, Aug 09 2018, from PARI *)
  • PARI
    {a(n)=local(P);if(n>=1, P=matrix(n,n,r,c,if(r>=c,(-c^2-c)^(r-c)/(r-c)!))); return(if(n<1,0,(P^-1)[n,1]*(n-1)!))}

Formula

For n>1: 0 = Sum_{k=1..n} C(n-1, k-1)*(-k^2-k)^(n-k)*a(k).

A103238 Triangular matrix T, read by rows, that satisfies: T^2 + T = SHIFTUP(T), also T^(n+1) + T^n = SHIFTUP(T^n - D*T^(n-1)) for all n, where D is a diagonal matrix with diagonal(D) = diagonal(T) = {1,2,3,...}.

Original entry on oeis.org

1, 2, 2, 8, 6, 3, 52, 36, 12, 4, 480, 324, 96, 20, 5, 5816, 3888, 1104, 200, 30, 6, 87936, 58536, 16320, 2800, 360, 42, 7, 1601728, 1064016, 294048, 49200, 5940, 588, 56, 8, 34251520, 22728384, 6252288, 1032800, 120960, 11172, 896, 72, 9, 843099616
Offset: 0

Views

Author

Paul D. Hanna, Jan 31 2005

Keywords

Comments

Leftmost column is A103239. The operation SHIFTUP(T) shifts each column of T up 1 row, dropping the elements that occupied the diagonal of T.

Examples

			Rows of T begin:
[1],
[2,2],
[8,6,3],
[52,36,12,4],
[480,324,96,20,5],
[5816,3888,1104,200,30,6],
[87936,58536,16320,2800,360,42,7],
[1601728,1064016,294048,49200,5940,588,56,8],...
Rows of T^2 begin:
[1],
[6,4],
[44,30,9],
[428,288,84,16],
[5336,3564,1008,180,25],...
Then T^2 + T = SHIFTUP(T):
[2],
[8,6],
[52,36,12],
[480,324,96,20],
[5816,3888,1104,200,30],...
G.f. for column 0: 1 = (1-2x) + 2*x/(1-x)*(1-2x)(1-3x) + 8*x^2/(1-x)^2*(1-2x)(1-3x)(1-4x) + 52*x^3/(1-x)^3*(1-2x)(1-3x)(1-4x)(1-5x) + ... + T(n,0)*x^n/(1-x)^n*(1-2x)(1-3x)*..*(1-(n+2)x) + ...
G.f. for column 1: 2 = 2*(1-3x) + 6*x/(1-x)*(1-3x)(1-4x) + 36*x^2/(1-x)^2*(1-3x)(1-4x)(1-5x) + 324*x^3/(1-x)^3*(1-3x)(1-4x)(1-5x)(1-6x) + ... + T(n,1)*x^(n-1)/(1-x)^(n-1)*(1-3x)(1-4x)*..*(1-(n+2)x) + ...
		

Crossrefs

Programs

  • PARI
    /* Using Matrix Diagonalization Formula: */ T(n,k)=my(P,D);D=matrix(n+1,n+1,r,c,if(r==c,r)); P=matrix(n+1,n+1,r,c,if(r>=c,(-1)^(r-c)*(c^2+c)^(r-c)/(r-c)!)); return(if(n
    				
  • PARI
    /* Using Generating Function for Columns: */ T(n,k)=if(n
    				

Formula

G.f. for column k: T(k, k) = k+1 = Sum_{n>=k} T(n, k)*x^(n-k)/(1-x)^(n-k) * Product_{j=0..n-k} (1-(j+k+2)*x). Diagonalization: T = P*D*P^-1 where P(r, c) = A103249(r, c)/(r-c)! = (-1)^(r-c)*(c^2+c)^(r-c)/(r-c)! for r>=c>=1 and [P^-1](r, c) = A103244(r, c)/(r-c)! and D is a diagonal matrix = {1, 2, 3, ...}.

A261642 Triangle, read by rows, where T(n,k) = (k^2 + k)^(n-k) for k=1..n and n>=1.

Original entry on oeis.org

1, 2, 1, 4, 6, 1, 8, 36, 12, 1, 16, 216, 144, 20, 1, 32, 1296, 1728, 400, 30, 1, 64, 7776, 20736, 8000, 900, 42, 1, 128, 46656, 248832, 160000, 27000, 1764, 56, 1, 256, 279936, 2985984, 3200000, 810000, 74088, 3136, 72, 1, 512, 1679616, 35831808, 64000000, 24300000, 3111696, 175616, 5184, 90, 1
Offset: 1

Views

Author

Paul D. Hanna, Aug 27 2015

Keywords

Comments

Matrix inverse of triangle P with element P(n,k) = (-1)^(n-k) * (k^2 + k)^(n-k) / (n-k)! forms triangle A103244.

Examples

			This triangle begins:
1;
2, 1;
4, 6, 1;
8, 36, 12, 1;
16, 216, 144, 20, 1;
32, 1296, 1728, 400, 30, 1;
64, 7776, 20736, 8000, 900, 42, 1;
128, 46656, 248832, 160000, 27000, 1764, 56, 1;
256, 279936, 2985984, 3200000, 810000, 74088, 3136, 72, 1;
512, 1679616, 35831808, 64000000, 24300000, 3111696, 175616, 5184, 90, 1;
1024, 10077696, 429981696, 1280000000, 729000000, 130691232, 9834496, 373248, 8100, 110, 1; ...
		

Crossrefs

Cf. A103244, A261643 (row sums).

Programs

  • PARI
    {T(n, k) = (k^2 + k)^(n-k)}
    for(n=1, 10, for(k=1, n, print1(T(n, k), ", ")); print(""))
Showing 1-3 of 3 results.