Even triangular numbers with prime indices.

Terms

a(0) =6a(1) =28a(2) =66a(3) =190a(4) =276a(5) =496a(6) =946a(7) =1128a(8) =1770a(9) =2278a(10) =2556a(11) =3160a(12) =3486a(13) =5356a(14) =5778a(15) =8128a(16) =8646a(17) =9730a(18) =11476a(19) =13366a(20) =14028a(21) =16110a(22) =18336a(23) =19900a(24) =22366a(25) =24976a(26) =25878a(27) =28680a(28) =31626a(29) =34716