Fancy primitive repdigit polygonal numbers.

Terms

a(0) =6a(1) =9a(2) =22a(3) =55a(4) =66a(5) =88a(6) =111a(7) =222a(8) =333a(9) =444a(10) =555a(11) =666a(12) =777a(13) =888a(14) =6666a(15) =44444a(16) =111111a(17) =777777a(18) =999999a(19) =111111111a(20) =777777777a(21) =9999999999a(22) =333333333333a(23) =555555555555