A331540 Number of primes of the form k*2^n + 1 with k < 2^n.

1, 2, 2, 5, 10, 16, 31, 47, 88, 149, 290, 536, 952, 1769, 3280, 6186, 11638, 21901, 41488, 78543, 149662, 284735, 543155, 1040577, 1994339, 3834731, 7373228, 14206331, 27405523, 52941914, 102381148

Offset

1,2

Comments

Both even and odd k are counted. Variant of A134876.

Links

Table of n, a(n) for n=1..31.

Prog

(PARI) a(n) = sum(k=1, 2^n-1, ispseudoprime(k<<n+1))

Crossrefs

Cf. A134876.

Sequence in context: A208788 A246864 A262924 * A329676 A247354 A317877

Adjacent sequences: A331537 A331538 A331539 * A331541 A331542 A331543

Keyword

nonn,more

Author

Jeppe Stig Nielsen, Jan 19 2020

Status

approved