A349820 Primes p such that 2*p is a member of A230624.

5, 7, 11, 19, 31, 47, 79, 103, 191, 239, 383, 479, 863, 991, 2687, 2879, 3391, 4799, 6719, 9343, 21503, 23039, 36607, 69119, 72959, 126719, 152063, 382463, 602111, 927743, 972799, 1096703, 1102847, 1640447, 1655807, 1966079, 3565567, 3590143, 4124671, 5402623

Offset: 1

Author

N. J. A. Sloane, Dec 30 2021

Keywords

• nonn

Comments

It is not known if A230624 is infinite. Many of its initial terms are twice primes, so it would interesting if these primes could be characterized in some other way.

a(n)+1 typically has a slowly growing power of 2 as factor. as can be seen here: (PARI) for(k=1, #a, print1(valuation(a[k]+1,2),", ")): 1, 3, 2, 2, 5, 4, 4, 3, 6, 4, 7, 5, 5, 5, 7, 6, 6, 6, 6, 7, 10, 9, 8, 9, 8, 8, 9, 9, 12, 11, 11, 10, 10, 11, 10, 17, 11, 11, 12, 12,.. - Hugo Pfoertner Jan 03 2022

Crossrefs

Cf. A230624, A349821.

Extensions

a(29)-a(40) from Martin Ehrenstein, Jan 03 2022