A331540 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A331540

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

%I #7 Jan 20 2020 12:51:57

%S 1,2,2,5,10,16,31,47,88,149,290,536,952,1769,3280,6186,11638,21901,

%T 41488,78543,149662,284735,543155,1040577,1994339,3834731,7373228,

%U 14206331,27405523,52941914,102381148

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

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

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

%Y Cf. A134876.

%K nonn,more

%O 1,2

%A _Jeppe Stig Nielsen_, Jan 19 2020