A366171 Integers k such that (2^(k+3)-2^k-1)/5 is prime.

3, 7, 19, 27, 31, 39, 151, 199, 451, 2371, 2511, 7859, 103819

Offset

1,1

Comments

If p = (2^(k+3)-2^k-1)/5 is prime, then 2^(k+2)*p is a strongly 2-near perfect number.

a(14) > 2*10^5. - Michael S. Branicky, Dec 02 2024

Links

Table of n, a(n) for n=1..13.

Vedant Aryan, Dev Madhavani, Savan Parikh, Ingrid Slattery, and Joshua Zelinsky, On 2-Near Perfect Numbers, arXiv:2310.01305 [math.NT], 2023. See p. 15.

Prog

(PARI) isok(k) = my(x=(2^(k+3)-2^k-1)/5); (denominator(x)==1) && ispseudoprime(x);

Crossrefs

Cf. A366172 (strongly 2-near perfect numbers).

Sequence in context: A001985 A203321 A203319 * A164097 A171140 A186452

Adjacent sequences: A366168 A366169 A366170 * A366172 A366173 A366174

Keyword

nonn,more

Author

Michel Marcus, Oct 03 2023

Extensions

a(13) from Michael S. Branicky, Oct 05 2023

Status

approved