Second pentagonal numbers with even index: a(n) = n*(6*n+1).

Terms

a(0) =0a(1) =7a(2) =26a(3) =57a(4) =100a(5) =155a(6) =222a(7) =301a(8) =392a(9) =495a(10) =610a(11) =737a(12) =876a(13) =1027a(14) =1190a(15) =1365a(16) =1552a(17) =1751a(18) =1962a(19) =2185a(20) =2420a(21) =2667a(22) =2926a(23) =3197a(24) =3480a(25) =3775a(26) =4082a(27) =4401a(28) =4732a(29) =5075