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

1,1

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

Links

Table of n, a(n) for n=1..40.

Crossrefs

Cf. A230624, A349821.

Sequence in context: A019376 A159080 A349821 * A227770 A038881 A190359

Adjacent sequences: A349817 A349818 A349819 * A349821 A349822 A349823

Keyword

nonn

Author

N. J. A. Sloane, Dec 30 2021

Extensions

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

Status

approved