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 1-2 of 2 results.

A134541 Triangle read by rows: A000012 * A054525 regarded as infinite lower triangular matrices.

Original entry on oeis.org

1, 0, 1, -1, 1, 1, -1, 0, 1, 1, -2, 0, 1, 1, 1, -1, -1, 0, 1, 1, 1, -2, -1, 0, 1, 1, 1, 1, -2, -1, 0, 0, 1, 1, 1, 1, -2, -1, -1, 0, 1, 1, 1, 1, 1, -1, -2, -1, 0, 0, 1, 1, 1, 1, 1, -2, -2, -1, 0, 0, 1, 1, 1, 1, 1, 1, -2, -1, -1, -1, 0, 0, 1, 1, 1, 1, 1, 1
Offset: 1

Views

Author

Gary W. Adamson, Oct 31 2007

Keywords

Comments

Row sums = 1.
Left border = A002321, the Mertens function.
A134541 * [1,2,3,...] = A002088: (1, 2, 4, 6, 10, 12, 18, 22, ...).

Examples

			First few rows of the triangle:
   1;
   0,  1;
  -1,  1,  1;
  -1,  0,  1, 1;
  -2,  0,  1, 1, 1;
  -1, -1,  0, 1, 1, 1;
  -2, -1,  0, 1, 1, 1, 1;
  -2, -1,  0, 0, 1, 1, 1, 1;
  -2, -1, -1, 0, 1, 1, 1, 1, 1;
  -1, -2, -1, 0, 0, 1, 1, 1, 1, 1;
  ...
		

Crossrefs

Matrix inverse of A176702. - Mats Granvik, Apr 24 2010

Programs

  • Mathematica
    Clear[t, s, n, k, z, x]; z = 1; nn = 10; t[n_, k_] := t[n, k] = If[n >= k, If[k == 1, 1 - Sum[t[n, k + i]/(i + 1)^(s - 1), {i, 1, n - 1}], t[Floor[n/k], 1]], 0]; Flatten[Table[Table[Limit[t[n, k], s -> z], {k, 1, n}], {n, 1, nn}]] (* Mats Granvik, Jul 22 2012 *) (* updated Mats Granvik, Apr 10 2016 *)

Formula

Recurrence: T(n, k) = If n >= k then If k = 1 then 1 - Sum_{i=1..n-1} T(n, k + i)/(i + 1)^(s - 1) else T(floor(n/k) else 1)) else 0). - Mats Granvik, Apr 17 2016

Extensions

More terms from Amiram Eldar, Jun 09 2024

A180430 Triangle T(n,k) defined by the recurrence in the formula.

Original entry on oeis.org

1, 1, 2, 1, 0, 2, 1, 2, -2, 2, 1, 0, 2, -2, 2, 1, 2, 0, 0, -2, 2, 1, 0, 0, 2, 0, -2, 2, 1, 2, 0, 0, 0, 0, -2, 2, 1, 0, 2, -2, 2, 0, 0, -2, 2, 1, 2, -2, 2, 0, 0, 0, 0, -2, 2, 1, 0, 2, 0, -2, 2, 0, 0, 0, -2, 2, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, -2, 2, 1, 0, 0, 0, 2, -2, 2, 0, 0, 0, 0, -2, 2, 1, 2, 0, 0, 0, 0, 0, 0
Offset: 1

Views

Author

Mats Granvik, Sep 04 2010

Keywords

Examples

			Table starts:
  1;
  1,  2;
  1,  0,  2;
  1,  2, -2,  2;
  1,  0,  2, -2,  2;
  1,  2,  0,  0, -2,  2;
  1,  0,  0,  2,  0, -2,  2;
  1,  2,  0,  0,  0,  0, -2,  2;
  1,  0,  2, -2,  2,  0,  0, -2,  2;
  1,  2, -2,  2,  0,  0,  0,  0, -2,  2;
		

Crossrefs

Cf. A176702.

Programs

  • Excel
    Using European dot comma style:
    =if(column()=1; 1; if(row()>=column(); sum(indirect(address(row()-column()+2; column()-1; 4)&":"&address(row()-1; column()-1; 4); 4))-sum(indirect(address(row()-column()+1; column(); 4)&":"&address(row()-1; column(); 4); 4)); 0))
  • Maple
    A180430 := proc(n,k) option remember; if k>n then 0; elif k = 1 then 1; elif k = 2 then 2-procname(n-1,k) ; else add( procname(n-i,k-1),i=1..k-2) - add(procname(n-i,k),i=1..k-1) ; end if; end proc: # R. J. Mathar, Jul 13 2011

Formula

T(n,1)=1. T(n,2) = 2-T(n-1,2). T(n,k) = Sum_{i=1..k-2} T(n-i,k-1) - Sum{i=1..k-1} T(n-i,k) for k > 2.
Showing 1-2 of 2 results.