A231966 Squarefree numbers (from A005117) with prime divisors in a 2p+1 progression.

10, 21, 55, 110, 253, 1081, 1265, 1711, 2530, 3403, 5671, 11891, 13861, 15931, 25651, 34453, 59455, 60031, 64261, 73153, 108811, 114481, 118910, 126253, 158203, 171991, 258121, 351541, 371953, 392941, 482653, 518671, 568301, 703891, 822403, 853471, 869221, 933661

Offset: 1

Author

Jaroslav Krizek, Nov 16 2013

Keywords

• nonn

Comments

Squarefree numbers with k>=2 prime divisors of the form p_1 * p_2 * … * p_k, where p_1 < p_2 < … < p_k = primes with p_k = 2 * p_(k-1) + 1.

Supersequence of A156592 (numbers of the form p*q, p and q prime with q=2*p+1; see A005384 and A005385).

Examples

			118910 = 2*5*11*23*47, where 5 = 2*2 + 1, 11 = 2*5 + 1, 23 = 2*11 + 1, 47 = 2*23 + 1.
		

Crossrefs

Cf. A005117, A156592, A005384, A005385, A000040, A231967, A231968, A231969.