A126253 a(n) = n-th integer from among those positive integers which are each coprime to exactly one prime dividing n.

3, 4, 7, 6, 10, 8, 15, 13, 18, 12, 22, 14, 26, 36, 31, 18, 34, 20, 38, 54, 42, 24, 46, 31, 50, 40, 54, 30, 130, 32, 63, 88, 66, 120, 70, 38, 74, 105, 78, 42, 192, 44, 86, 111, 90, 48, 94, 57, 98, 141, 102, 54, 106, 210, 110, 159, 114, 60, 255, 62, 122, 162

Offset: 2

Author

Leroy Quet, Mar 08 2007

Keywords

• nonn

Examples

			The positive integers which are each coprime to exactly one prime dividing 12 form the sequence: 2,3,4,8,9,10,14,15,16,20,21,22,26,27,28... The 12th of these is 22; so a(12) = 22.
		

Crossrefs

Cf. A125704, A128487.

Programs

PARI

a(n) = {ok = 0; nb = 0; i = 1; pf = factor(n)[,1]; while(! ok, if (sum(j=1, #pf, gcd(i, pf[j]) == 1) == 1, nb++); if (nb == n, ok = 1, i++);); i;} \\ Michel Marcus, Feb 10 2014

Extensions

Offset corrected and more terms from Michel Marcus, Feb 10 2014