k such that 2kp+1 is the first factor of a nonprime Mersenne number M(p) = 2^p - 1.

Terms

a(0) =1a(1) =1a(2) =4a(3) =3a(4) =163a(5) =5a(6) =25a(7) =60a(8) =1525a(9) =1445580a(10) =1609a(11) =3a(12) =17a(13) =1a(14) =59a(15) =36793758459a(16) =12379533a(17) =3421967a(18) =15a(19) =1a(21) =20236572837a(23) =60a(24) =2713800a(25) =461a(26) =7033a(27) =2112a(28) =1a(29) =120a(30) =1a(31) =35807