Numbers k such that the k-th triangular number contains only digits {2,5,6}.

Terms

a(0) =3a(1) =10a(2) =11a(3) =36a(4) =71a(5) =105a(6) =114a(7) =230a(8) =714a(9) =2128a(10) =3363a(11) =10550a(12) =32411a(13) =73010a(14) =2309210a(15) =3648430a(16) =10641950a(17) =23045894a(18) =33336636a(19) =72479825a(20) =111581563a(21) =229156071a(22) =36118284988a(23) =730103037471