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.

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, 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, 3, 2, 1, 13, 18, 12, 12, 8, 7, 6, 5, 4, 3, 2, 1, 14, 20

Offset

1,1

Comments

Column k lists the numbers j such that A000005(j) <> k.

Links

Table of n, a(n) for n=1..80.

Example

Column 2 lists the nonprimes A018252 because they are the positive integers whose number of divisors is not 2.
Array begins:
2,   1,  1,  1,  1,  1,  1,  1,  1,  1,
3,   4,  2,  2,  2,  2,  2,  2,  2,
4,   6,  3,  3,  3,  3,  3,  3,
5,   8,  5,  4,  4,  4,  4,
6,   9,  6,  5,  5,  5,
7,  10,  7,  7,  6,
8,  12,  8,  9,
9,  14, 10,
10, 15,
11,

Crossrefs

Columns (1-4): A020725, A018252, A213367, A210994.

Sequence in context: A201927 A238442 A090244 * A258263 A096180 A354265

Adjacent sequences: A210973 A210974 A210975 * A210977 A210978 A210979

Keyword

nonn,tabl

Author

Omar E. Pol, Aug 11 2012

Status

approved