Even pentagonal numbers.

Terms

a(0) =0a(1) =12a(2) =22a(3) =70a(4) =92a(5) =176a(6) =210a(7) =330a(8) =376a(9) =532a(10) =590a(11) =782a(12) =852a(13) =1080a(14) =1162a(15) =1426a(16) =1520a(17) =1820a(18) =1926a(19) =2262a(20) =2380a(21) =2752a(22) =2882a(23) =3290a(24) =3432a(25) =3876a(26) =4030a(27) =4510a(28) =4676a(29) =5192