Triangular numbers that differ from a square by 1.

Terms

a(0) =0a(1) =1a(2) =3a(3) =10a(4) =15a(5) =120a(6) =325a(7) =528a(8) =4095a(9) =11026a(10) =17955a(11) =139128a(12) =374545a(13) =609960a(14) =4726275a(15) =12723490a(16) =20720703a(17) =160554240a(18) =432224101a(19) =703893960a(20) =5454117903a(21) =14682895930a(22) =23911673955a(23) =185279454480a(24) =498786237505a(25) =812293020528