Indices k such that 8 plus the k-th triangular number is a perfect square.

Terms

a(0) =1a(1) =7a(2) =16a(3) =46a(4) =97a(5) =271a(6) =568a(7) =1582a(8) =3313a(9) =9223a(10) =19312a(11) =53758a(12) =112561a(13) =313327a(14) =656056a(15) =1826206a(16) =3823777a(17) =10643911a(18) =22286608a(19) =62037262a(20) =129895873a(21) =361579663a(22) =757088632a(23) =2107440718a(24) =4412635921a(25) =12283064647a(26) =25718726896a(27) =71590947166a(28) =149899725457a(29) =417262618351