Indices of primes in A001644 (the Lucas 3-step numbers).

Terms

a(0) =2a(1) =3a(2) =4a(3) =7a(4) =8a(5) =9a(6) =10a(7) =12a(8) =20a(9) =30a(10) =33a(11) =66a(12) =76a(13) =77a(14) =82a(15) =87a(16) =98a(17) =180a(18) =205a(19) =360a(20) =553a(21) =719a(22) =766a(23) =1390a(24) =1879a(25) =1999a(26) =4033a(27) =5620a(28) =16506a(29) =17436