cp's OEIS Frontend

A210976 Square array T(n,k), n>=1, k>=1, read by antidiagonals in which column k lists the positive integers whose number of divisors is not k.

%I A210976 #13 Aug 11 2012 22:03:57
%S A210976 2,3,1,4,4,1,5,6,2,1,6,8,3,2,1,7,9,5,3,2,1,8,10,6,4,3,2,1,9,12,7,5,4,
%T A210976 3,2,1,10,14,8,7,5,4,3,2,1,11,15,10,9,6,5,4,3,2,1,12,16,11,11,7,6,5,4,
%U A210976 3,2,1,13,18,12,12,8,7,6,5,4,3,2,1,14,20
%N A210976 Square array T(n,k), n>=1, k>=1, read by antidiagonals in which column k lists the positive integers whose number of divisors is not k.
%C A210976 Column k lists the numbers j such that A000005(j) <> k.
%e A210976 Column 2 lists the nonprimes A018252 because they are the positive integers whose number of divisors is not 2.
%e A210976 Array begins:
%e A210976 2,   1,  1,  1,  1,  1,  1,  1,  1,  1,
%e A210976 3,   4,  2,  2,  2,  2,  2,  2,  2,
%e A210976 4,   6,  3,  3,  3,  3,  3,  3,
%e A210976 5,   8,  5,  4,  4,  4,  4,
%e A210976 6,   9,  6,  5,  5,  5,
%e A210976 7,  10,  7,  7,  6,
%e A210976 8,  12,  8,  9,
%e A210976 9,  14, 10,
%e A210976 10, 15,
%e A210976 11,
%Y A210976 Columns (1-4): A020725, A018252, A213367, A210994.
%K A210976 nonn,tabl
%O A210976 1,1
%A A210976 _Omar E. Pol_, Aug 11 2012