A131432 - OEIS

%I #10 Jun 05 2023 05:22:46

%S 1,4,7,7,10,13,10,13,16,19,13,16,19,22,25,16,19,22,25,28,31,19,22,25,

%T 28,31,34,37,22,25,28,31,34,37,40,43,25,28,31,34,37,40,43,46,49,28,31,

%U 34,37,40,43,46,49,52,55,31,34,37,40,43,46,49,52,55,58,61,34,37,40,43,46,49,52,55,58,61,64,67

%N Triangle read by rows: (A000012 * A131431) + (A131431 * A000012) - A000012 as infinite lower triangular matrices.

%C Left border = A016777, (1, 4, 7, 10, 13, ...).

%C Right border = A016921: (1, 7, 13, 19, 25, ...).

%C Row sums = A051682, 11-gonal numbers: (1, 11, 30, 58, 95, ...).

%e First few rows of the triangle:

%e    1;

%e    4,  7;

%e    7, 10, 13;

%e   10, 13, 16, 19;

%e   13, 16, 19, 22, 25;

%e   16, 19, 22, 25, 28, 31;

%e   19, 22, 25, 28, 31, 34, 37;

%e   ...

%Y Cf. A016777, A051682, A131431, A016921.

%K nonn,tabl

%O 0,2

%A _Gary W. Adamson_, Jul 10 2007

%E a(28) ff. corrected and more terms from _Georg Fischer_, Jun 05 2023