A331540 - OEIS

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A331540

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

1

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

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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

Sequence in context: A262924 A392702 A389601 * A329676 A391595 A247354

Adjacent sequences: A331537 A331538 A331539 * A331541 A331542 A331543

KEYWORD

nonn,more

AUTHOR

Jeppe Stig Nielsen, Jan 19 2020

STATUS

approved