a(n) = position of n^2 + (n+1)^2 in A004431 (sums of 2 distinct nonzero squares).

Terms

a(0) =1a(1) =3a(2) =6a(3) =12a(4) =18a(5) =25a(6) =34a(7) =42a(8) =55a(9) =66a(10) =80a(11) =94a(12) =110a(13) =127a(14) =144a(15) =162a(16) =183a(17) =204a(18) =224a(19) =248a(20) =272a(21) =296a(22) =322a(23) =348a(24) =378a(25) =407a(26) =434a(27) =469a(28) =500a(29) =533