A339307 Numbers k such that A228553(k) is prime.

11, 20, 24, 27, 32, 35, 37, 38, 68, 74, 78, 79, 82, 96, 98, 101, 103, 122, 137, 149, 161, 188, 209, 218, 239, 249, 258, 276, 293, 321, 325, 333, 363, 365, 372, 433, 445, 449, 499, 535, 567, 568, 580, 588, 594, 595, 622, 644, 656, 663, 666, 682, 688, 693, 721, 742, 754, 756, 760, 796, 814, 845

Offset: 1

Author

J. M. Bergot and Robert Israel, Nov 29 2020

Keywords

• nonn

Examples

			a(3) = 24 is in the sequence because A228553(24) = 1987 is prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A228553, A339309.

Programs

Maple

f:= proc(n)
  local S;
  S:= select(t -> isprime(t) and isprime(2*n-t), [seq(i,i=3..n,2)]);
  add(t*(2*n-t),t=S)
end proc:
f(2):= 4:
select(isprime@f, [$1..1000]);