A134001 Array read by antidiagonals: row n contains the positive integers each with exactly n positive "isolated divisors". A divisor, k, of n is isolated if neither (k-1) nor (k+1) divides n.

3, 9, 5, 15, 16, 7, 36, 21, 18, 8, 45, 54, 24, 25, 10, 126, 48, 64, 27, 30, 11, 96, 150, 60, 66, 28, 42, 12, 144, 105, 162, 63, 78, 32, 49, 13, 120, 168, 108, 196, 70, 81, 33, 121, 14, 324, 180, 198, 135, 256, 72, 90, 35, 169, 17, 240, 378, 192, 225, 140, 294, 75, 100, 39

Offset

2,1

Comments

The left column (column 1) of the array is sequence A133997. The array starts at column 1 and row 2. The only positive integers each with exactly 1 isolated divisor are 1,4,6.

Links

Table of n, a(n) for n=2..65.

Example

2 isolated divisors:  3,  5,  7,  8, 10, ...
3 isolated divisors:  9, 16, 18, 25, ...
4 isolated divisors: 15, 21, 24, ...
etc.

Crossrefs

Cf. A133997, A134000.

Sequence in context: A064471 A264798 A054509 * A338350 A088898 A143218

Adjacent sequences: A133998 A133999 A134000 * A134002 A134003 A134004

Keyword

nonn,tabl

Author

Leroy Quet, Oct 01 2007

Extensions

Extended by Ray Chandler, Jun 25 2008

Status

approved