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 A043309 #8 Feb 03 2014 12:33:46 %S A043309 1,2,3,4,25,27,28,29,50,51,53,54,75,76,77,79,100,101,102,103,626,627, %T A043309 628,629,675,676,678,679,700,701,702,704,725,726,727,728,1251,1252, %U A043309 1253,1254,1275,1277,1278,1279,1325,1326,1327,1329 %N A043309 a(n)=A033003(n)/6. %C A043309 Also: Numbers which, written in base 25, have all digits less than 5 and no two adjacent digits equal. - _M. F. Hasler_, Feb 03 2014 %o A043309 (PARI) is_A043309(n)=(n=[n])&&!until(!n[1],((n=divrem(n[1],25))[2]<5 && n[1]%5!=n[2])||return) \\ _M. F. Hasler_, Feb 03 2014 %Y A043309 Cf. A043307 - A043320, A043291, A033001 - A033014, A033016 - A033029. %K A043309 nonn,base %O A043309 1,2 %A A043309 _Clark Kimberling_