A127471 - OEIS

%I #17 May 29 2023 13:03:40

%S 1,2,1,2,0,2,3,2,0,2,2,0,0,0,4,4,2,4,0,0,2,2,0,0,0,0,0,6,4,3,0,4,0,0,

%T 0,4,3,0,4,0,0,0,0,0,6,4,2,0,0,8,0,0,0,0,4,2,0,0,0,0,0,0,0,0,0,10,6,4,

%U 6,4,0,4,0,0,0,0,0,4,2,0,0,0,0,0,0,0,0,0,0,0,12

%N Triangle formed from the matrix product A051731 * A054522 of infinite lower triangular matrices, read by rows.

%C Left column = (1, 2, 2, 3, 2, 4, ...) = d(n), A000005; right border = (1, 1, 2, 2, 4, 2, 6, ...) = phi(n), A000010; row sums = (1, 3, 4, 7, 6, 12, ...) = sigma(n), A000203.

%e First few rows of the triangle:

%e   1;

%e   2, 1;

%e   2, 0, 2;

%e   3, 2, 0, 2;

%e   2, 0, 0, 0, 4;

%e   4, 2, 4, 0, 0, 2;

%e   2, 0, 0, 0, 0, 0, 6;

%e   4, 3, 0, 4, 0, 0, 0, 4;

%e   3, 0, 4, 0, 0, 0, 0, 0, 6;

%e   4, 2, 0, 0, 8, 0, 0, 0, 0, 4;

%e   ...

%Y Cf. A000005, A000010, A000203, A051731, A054522.

%K nonn,tabl

%O 1,2

%A _Gary W. Adamson_, Jan 15 2007

%E Edited by _N. J. A. Sloane_, Aug 11 2019

%E a(49) = 0 inserted and more terms from _Georg Fischer_, May 29 2023