a(n) is the least exponent k such that 3^k-1 is divisible by prime(n)^2, or -1 if no such k exists.

Terms

a(0) =2a(1) =-1a(2) =20a(3) =42a(4) =5a(5) =39a(6) =272a(7) =342a(8) =253a(9) =812a(10) =930a(11) =666a(12) =328a(13) =1806a(14) =1081a(15) =2756a(16) =1711a(17) =610a(18) =1474a(19) =2485a(20) =876a(21) =6162a(22) =3403a(23) =7832a(24) =4656a(25) =10100a(26) =3502a(27) =5671a(28) =2943a(29) =12656