Smallest k such that k*Mersenne_prime(n)^2 -1 (or k*A000668(n)^2 -1) is prime.

Terms

a(0) =2a(1) =2a(2) =8a(3) =2a(4) =12a(5) =2a(6) =2a(7) =98a(8) =38a(9) =122a(10) =126a(11) =678a(12) =440a(13) =1040a(14) =776a(15) =1398a(16) =2714a(17) =3362a(18) =650a(19) =8910a(20) =22010a(21) =11172a(22) =1422a(23) =5274a(24) =33944a(25) =4508a(26) =12614a(27) =202298a(28) =275466