Indices of triangular numbers that are one-tenth of other triangular numbers.

Terms

a(0) =0a(1) =1a(2) =6a(3) =12a(4) =55a(5) =246a(6) =474a(7) =2107a(8) =9360a(9) =18018a(10) =80029a(11) =355452a(12) =684228a(13) =3039013a(14) =13497834a(15) =25982664a(16) =115402483a(17) =512562258a(18) =986657022a(19) =4382255359a(20) =19463867988a(21) =37466984190a(22) =166410301177a(23) =739114421304