Triangular numbers obtained as a concatenation of successive terms of A081847.

Terms

a(0) =15a(1) =55a(2) =528a(3) =2850a(4) =5050a(5) =50403a(6) =403651a(7) =651511a(8) =511566a(9) =56616a(10) =1653a(11) =5356a(12) =561a(13) =120a(14) =2016a(15) =16110a(16) =11026a(17) =2628a(18) =28203a(19) =203203a(20) =203841a(21) =841753a(22) =753378a(23) =378885a(24) =885115a(25) =115440a(26) =440391a(27) =3916a(28) =66a(29) =630