Triangular numbers T such that both (T+2) and (T-2) are semiprimes.

Terms

a(0) =36a(1) =120a(2) =276a(3) =300a(4) =325a(5) =903a(6) =1653a(7) =2485a(8) =2556a(9) =3240a(10) =4851a(11) =5253a(12) =5460a(13) =5995a(14) =6105a(15) =6441a(16) =6903a(17) =8001a(18) =8256a(19) =8911a(20) =9591a(21) =10585a(22) =12561a(23) =12720a(24) =14365a(25) =20301a(26) =21115a(27) =22791a(28) =23436a(29) =24753