a(n) = smallest prime p such that p-1 and p+1 together have n prime divisors, or a(n) = 0 if no such prime exists.
A155800
a(n) = smallest prime p such that p-1 and p+1 together have n prime divisors, or a(n) = 0 if no such prime exists.
Terms
- a(0) =2a(1) =0a(2) =3a(3) =5a(4) =7a(5) =19a(6) =17a(7) =31a(8) =97a(9) =191a(10) =127a(11) =449a(12) =769a(13) =3329a(14) =6143a(15) =7937a(16) =12799a(17) =51199a(18) =8191a(19) =165887a(20) =65537a(21) =131071a(22) =1179649a(23) =2654209a(24) =7995391a(25) =524287a(26) =10616831a(27) =12910591a(28) =167772161a(29) =113246209
External references
- oeis: A155800