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A128228 A128229 * A002260. 3
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 (list; table; graph; refs; listen; history; text; internal format)
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

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Last modified June 18 15:25 EDT 2019. Contains 324213 sequences. (Running on oeis4.)