Triangular numbers for which the sum of the digits is a heptagonal number.

Terms

a(0) =0a(1) =1a(2) =10a(3) =378a(4) =666a(5) =990a(6) =1485a(7) =1953a(8) =2556a(9) =2628a(10) =4095a(11) =4851a(12) =4950a(13) =6903a(14) =9045a(15) =9180a(16) =10296a(17) =11628a(18) =11781a(19) =14535a(20) =14706a(21) =16290a(22) =19503a(23) =19701a(24) =21528a(25) =23436a(26) =25425a(27) =27261a(28) =29403a(29) =31626