Indices k such that 3 plus the k-th triangular number is a perfect square.

Terms

a(0) =1a(1) =3a(2) =12a(3) =22a(4) =73a(5) =131a(6) =428a(7) =766a(8) =2497a(9) =4467a(10) =14556a(11) =26038a(12) =84841a(13) =151763a(14) =494492a(15) =884542a(16) =2882113a(17) =5155491a(18) =16798188a(19) =30048406a(20) =97907017a(21) =175134947a(22) =570643916a(23) =1020761278a(24) =3325956481a(25) =5949432723a(26) =19385094972a(27) =34675835062a(28) =112984613353