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A128228 A128229 * A002260. 3

%I

%S 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,

%T 8,16,24,32,40,48,56,8,9,18,27,36,45,54,63,72,9,10,20,30,40,50,60,70,

%U 80,90,10

%N A128229 * A002260.

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

%F A128229 * A002260 as infinite lower triangular matrices.

%F Triangle, n * (each term of A128227).

%F T(n,k) = k*n if 1<=k<n, and T(n,n) = n. - _Hartmut F. W. Hoft_, Jun 10 2017

%e First few rows of the triangle are:

%e 1;

%e 2, 2;

%e 3, 6, 3;

%e 4, 8, 12, 4;

%e 5, 10, 15, 20, 5;

%e 6, 12, 18, 24, 30, 6;

%e 7, 14, 21, 28, 35, 42, 7;

%e ...

%t (* first n rows of the triangle *)

%t a128228[n_] := Table[If[r==q, r, q r], {r, 1, n}, {q, 1, r}]

%t Flatten[a128228[10]] (* data *)

%t TableForm[a128228[7]] (* triangle *)

%t (* _Hartmut F. W. Hoft_, Jun 10 2017 *)

%Y Cf. A128229, A002260, A006000, A128227.

%K nonn,tabl

%O 1,2

%A _Gary W. Adamson_, Feb 19 2007

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Last modified July 23 20:56 EDT 2019. Contains 325265 sequences. (Running on oeis4.)