This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A023802 #20 Feb 22 2019 06:02:55 %S A023802 0,1,2,3,4,5,6,7,9,10,11,12,13,14,15,17,18,19,20,21,22,23,25,26,27,28, %T A023802 29,30,31,33,34,35,36,37,38,39,41,42,43,44,45,46,47,51,52,53,54,55,63, %U A023802 66,67,68,69,70,72,74,75,76,77,79,80,82,83,84,86,87,88,90 %N A023802 Xenodromes: all digits in base 7 are different. %H A023802 Nathaniel Johnston, <a href="/A023802/b023802.txt">Table of n, a(n) for n = 1..11743</a> (full sequence) %e A023802 4146 in base 7 is 15042. Since no two digits of the base 7 representation are the same, 4146 is in the sequence. %e A023802 4147 in base 7 is 15043. Since no two digits of the base 7 representation are the same, 4147 is in the sequence. %e A023802 4148 in base 7 is 15044. Since the digit 4 appears twice in the base 7 representation, 4148 is not in the sequence. %t A023802 Select[Range[0, 97], Max[DigitCount[#, 7]] == 1 &] (* _Alonso del Arte_, Feb 09 2019 *) %o A023802 (PARI) isok(n) = my(d=digits(n, 7)); #d == #Set(d); \\ _Michel Marcus_, Feb 09 2019 %Y A023802 Cf. A023798 - A023810. %Y A023802 Cf. A007093 (numbers in base 7). %Y A023802 Cf. A044956 (includes a subset of the complement of this sequence). %K A023802 nonn,base,fini,full,easy %O A023802 1,3 %A A023802 _Olivier Gérard_