Indices k such that 26 plus the k-th triangular number is a perfect square.

Terms

a(0) =4a(1) =10a(2) =37a(3) =67a(4) =220a(5) =394a(6) =1285a(7) =2299a(8) =7492a(9) =13402a(10) =43669a(11) =78115a(12) =254524a(13) =455290a(14) =1483477a(15) =2653627a(16) =8646340a(17) =15466474a(18) =50394565a(19) =90145219a(20) =293721052a(21) =525404842a(22) =1711931749a(23) =3062283835a(24) =9977869444a(25) =17848298170a(26) =58155284917a(27) =104027505187a(28) =338953840060