Mersenne prime indices that are not Gaussian primes.

Terms

a(0) =2a(1) =5a(2) =13a(3) =17a(4) =61a(5) =89a(6) =521a(7) =2281a(8) =3217a(9) =4253a(10) =9689a(11) =9941a(12) =11213a(13) =19937a(14) =21701a(15) =23209a(16) =44497a(17) =132049a(18) =859433a(19) =1398269a(20) =2976221a(21) =3021377a(22) =6972593a(23) =13466917a(24) =30402457a(25) =32582657a(26) =42643801a(27) =43112609a(28) =57885161