Numbers k such that 4^k + 1 is a semiprime.

Terms

a(0) =3a(1) =6a(2) =10a(3) =14a(4) =16a(5) =20a(6) =32a(7) =46a(8) =52a(9) =64a(10) =74a(11) =128a(12) =178a(13) =298a(14) =346a(15) =502a(16) =614a(17) =634a(18) =1912a(19) =60394a(20) =92116