A128228 A128229 * A002260.

1, 2, 2, 3, 6, 3, 4, 8, 12, 4, 5, 10, 15, 20, 5, 6, 12, 18, 24, 30, 6, 7, 14, 21, 28, 35, 42, 7, 8, 16, 24, 32, 40, 48, 56, 8, 9, 18, 27, 36, 45, 54, 63, 72, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 10

Offset

1,2

Comments

Row sums = A006000: (1, 4, 12, 28, 55, 96, 154,...).

Links

Table of n, a(n) for n=1..55.

Formula

A128229 * A002260 as infinite lower triangular matrices.

Triangle, n * (each term of A128227).

T(n,k) = k*n if 1<=k<n, and T(n,n) = n. - Hartmut F. W. Hoft, Jun 10 2017

Example

First few rows of the triangle are:
1;
2, 2;
3, 6, 3;
4, 8, 12, 4;
5, 10, 15, 20, 5;
6, 12, 18, 24, 30, 6;
7, 14, 21, 28, 35, 42, 7;
...

Mathematica

(* first n rows of the triangle *)
a128228[n_] := Table[If[r==q, r, q r], {r, 1, n}, {q, 1, r}]
Flatten[a128228[10]] (* data *)
TableForm[a128228[7]] (* triangle *)
(* Hartmut F. W. Hoft, Jun 10 2017 *)

Crossrefs

Cf. A128229, A002260, A006000, A128227.

Sequence in context: A064426 A051173 A322744 * A190098 A272973 A272958

Adjacent sequences: A128225 A128226 A128227 * A128229 A128230 A128231

Keyword

nonn,tabl

Author

Gary W. Adamson, Feb 19 2007

Status

approved