Numbers n = 5*k^2 such that n - 1 and n + 1 are (twin) primes (thus k=6*m).

Terms

a(0) =180a(1) =1620a(2) =8820a(3) =35280a(4) =87120a(5) =151380a(6) =302580a(7) =380880a(8) =691920a(9) =737280a(10) =808020a(11) =1393920a(12) =5020020a(13) =5767380a(14) =7712820a(15) =9604980a(16) =10281780a(17) =11160180a(18) =12450420a(19) =12736080a(20) =14723280a(21) =15138000a(22) =17186580a(23) =17860500a(24) =18663120a(25) =18779220a(26) =19129680a(27) =21300480