Triangular numbers composed of digits {1,6,7}.

Terms

a(0) =1a(1) =6a(2) =66a(3) =171a(4) =666a(5) =1176a(6) =1711a(7) =17766a(8) =61776a(9) =67161a(10) =166176a(11) =617716a(12) =7767711a(13) =61677171a(14) =77171676a(15) =161667171a(16) =166777716a(17) =611677776a(18) =66767167176a(19) =77111161116a(20) =171676611666a(21) =617617761166