A210651 a(n)=least odd number k such that 3*k*2^n-1 is a prime number.

1, 1, 1, 1, 5, 1, 1, 9, 15, 5, 1, 29, 3, 5, 3, 15, 5, 1, 17, 19, 3, 11, 23, 13, 19, 19, 7, 9, 15, 71, 5, 19, 49, 1, 11, 15, 7, 1, 21, 39, 5, 11, 1, 19, 55, 11, 71, 39, 23, 29, 7, 61, 49, 15, 1, 11, 17, 37, 15, 31, 23, 19, 3, 1, 33, 21, 37, 21, 17, 9, 41, 43, 5, 7, 25, 1, 19, 37, 23, 5, 27, 5, 37, 31, 15, 85, 67, 43, 79, 77

Offset: 1

Author

Pierre CAMI, Mar 27 2012

Keywords

• nonn

Links

• Pierre CAMI, Table of n, a(n) for n = 1..7725

Crossrefs

Cf. A126717.

Programs

Maple

A210651 := proc(n)
        for k from 1 by 2 do
                if isprime(3*k*2^n-1) then
                        return k;
                end if;
        end do:
end proc: # R. J. Mathar, Mar 29 2012