A070799 Numbers of the form 6jk-j-k.

4, 9, 14, 19, 20, 24, 29, 31, 34, 39, 42, 44, 48, 49, 53, 54, 59, 64, 65, 69, 74, 75, 79, 82, 84, 86, 88, 89, 94, 97, 99, 104, 108, 109, 111, 114, 116, 119, 124, 129, 130, 133, 134, 139, 140, 141, 144, 149, 150, 152, 154, 157, 159, 163, 164, 167, 169, 174, 179, 180

Offset: 1

Author

Jon Perry, May 05 2002

Keywords

• nonn

Comments

Equivalently, numbers n such that 6n+1 has a factor == 5 (mod 6).

These numbers, together with numbers of the form 6jk+j+k (A070043) are the numbers n for which 6n+1 is composite (A046954). If we also add in the numbers of the form 6jk+j-k (A046953), we get the numbers n such that 6n-1 and 6n+1 do not form a pair of twin primes (A067611).

Examples

			31 = 6*2*3 - 2 - 3. Equivalently, 6*31+1 = (6*2-1)*(6*3-1).
		

Crossrefs

Cf. A070043, A046953, A046954, A067611.

Programs

Mathematica

Select[Range[250], MemberQ[Mod[Take[Divisors[6#+1], {2, -2}], 6], 5]&]

Extensions

Edited by Dean Hickerson, May 07 2002