Numbers k such that k!/m! is a triangular number for some m < k-1.

Terms

a(0) =3a(1) =5a(2) =6a(3) =7a(4) =11a(5) =14a(6) =15a(7) =58a(8) =85a(9) =493a(10) =638a(11) =2871a(12) =16731a(13) =97513a(14) =568345a(15) =3312555a(16) =19306983a(17) =112529341a(18) =655869061a(19) =3822685023a(20) =22280241075a(21) =129858761425a(22) =756872327473