Numbers whose reciprocals have a palindromic repeating part in base 7.
2, 3, 6, 14, 21, 42, 98, 147, 294, 686, 1029, 2058, 4802, 7203, 14406, 33614, 50421, 100842, 235298, 352947, 705894
1
All palindromes appear to be just one digit. These numbers appear to be (2, 3, 6) * 7^(i-1) for i = 1, 2, 3,….
T. D. Noe, Plot of 21 terms
Wikipedia, Repeating decimal
(Mma) Select[Range[7^5], (r = RealDigits[1/#, 7]; ! IntegerQ[r[[1, 1]]] && r[[1, 1]] == Reverse[r[[1, 1]]]) &]
nonn,base
T. D. Noe, Jun 03 2016