cp's OEIS Frontend

A280348 Irregular triangle read by rows in which row n lists the divisors of the sum of the divisors of n.

%I A280348 #19 Dec 11 2024 06:26:26
%S A280348 1,1,3,1,2,4,1,7,1,2,3,6,1,2,3,4,6,12,1,2,4,8,1,3,5,15,1,13,1,2,3,6,9,
%T A280348 18,1,2,3,4,6,12,1,2,4,7,14,28,1,2,7,14,1,2,3,4,6,8,12,24,1,2,3,4,6,8,
%U A280348 12,24,1,31,1,2,3,6,9,18,1,3,13,39,1,2,4,5,10,20,1,2,3,6,7,14,21,42,1,2,4,8,16,32,1,2,3,4,6,9,12,18,36
%N A280348 Irregular triangle read by rows in which row n lists the divisors of the sum of the divisors of n.
%H A280348 Paolo Xausa, <a href="/A280348/b280348.txt">Table of n, a(n) for n = 1..11428</a> (rows 1..700 of triangle, flattened).
%F A280348 T(n,k) = A027750(A000203(n),k).
%e A280348 Triangle begins:
%e A280348 1;
%e A280348 1, 3;
%e A280348 1, 2, 4;
%e A280348 1, 7;
%e A280348 1, 2, 3, 6;
%e A280348 1, 2, 3, 4, 6, 12;
%e A280348 1, 2, 4, 8;
%e A280348 1, 3, 5, 15;
%e A280348 1, 13;
%e A280348 1, 2, 3, 6, 9, 18;
%e A280348 1, 2, 3, 4, 6, 12;
%e A280348 1, 2, 4, 7, 14, 28;
%e A280348 1, 2, 7, 14;
%e A280348 1, 2, 3, 4, 6, 8, 12, 24;
%e A280348 1, 2, 3, 4, 6, 8, 12, 24;
%e A280348 1, 31;
%e A280348 1, 2, 3, 6, 9, 18;
%e A280348 1, 3, 13, 39;
%e A280348 1, 2, 4, 5, 10, 20;
%e A280348 1, 2, 3, 6, 7, 14, 21, 42;
%e A280348 1, 2, 4, 8, 16, 32;
%e A280348 1, 2, 3, 4, 6, 9, 12, 18, 36;
%e A280348 1, 2, 3, 4, 6, 8, 12, 24;
%e A280348 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60;
%e A280348 ...
%e A280348 For n = 10 the sum of the divisors of 10 is 1 + 2 + 5 + 10 = 18, so row 10 of the triangle lists the divisors of 18: 1, 2, 3, 6, 9, 18.
%t A280348 Divisors[DivisorSigma[1, Range[25]]] (* _Paolo Xausa_, Dec 11 2024 *)
%Y A280348 Right border gives A000203.
%Y A280348 Row sums give A051027.
%Y A280348 Row lengths give A062068.
%Y A280348 Row products give A280581.
%Y A280348 Column 1 is A000012.
%Y A280348 Column 2 gives A071189, n >= 2.
%Y A280348 Cf. A000005, A027750.
%K A280348 nonn,tabf
%O A280348 1,3
%A A280348 _Omar E. Pol_, Jan 09 2017