Smallest number k > 0 such that sigma(x) and sigma(x)+2 are both prime, where x = (6k+1)^(6n+4), or -1 if no such k exists.
A275237
Smallest number k > 0 such that sigma(x) and sigma(x)+2 are both prime, where x = (6k+1)^(6n+4), or -1 if no such k exists.
Terms
- a(0) =1a(1) =348a(2) =436a(3) =6018a(4) =5880a(5) =-1a(6) =4612a(7) =26921a(8) =16166a(9) =81111a(10) =-1a(11) =426260a(12) =-1a(13) =181876a(14) =227180a(15) =-1a(16) =12836a(17) =287388a(18) =2317a(19) =-1a(20) =-1a(21) =1128403a(22) =668927a(23) =-1a(24) =5295a(25) =-1a(26) =-1a(27) =490118a(28) =2217967a(29) =1607226
External references
- oeis: A275237