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 A299985 #5 Feb 23 2018 09:49:09
%S A299985 0,5,10,15,20,25,26,9,6,19,16,29,21,4,1,14,11,24,27,8,7,18,17,28,22,3,
%T A299985 2,13,12,23,30,35,40,45,50,55,60,65,70,75,76,39,36,49,46,59,56,69,66,
%U A299985 79,71,34,31,44,41,54,51,64,61,74,77,38,37,48,47,58,57,68,67,78,72,33,32,43,42,53,52,63,62,73,80,85,90,95,100,105,110,115,120
%N A299985 Lexicographic first sequence of nonnegative integers such that a(n) + a(n+1) has a digit 5, and no term occurs twice.
%C A299985 A permutation of the nonnegative integers.
%o A299985 (PARI) a(n,f=1,d=5,a=0,u=[a])={for(n=1,n,f&&if(f==1,print1(a","),write(f,n-1," "a));for(k=u[1]+1,oo,setsearch(u,k)&&next;setsearch(Set(digits(a+k)),d)&&(a=k)&&break);u=setunion(u,[a]);u[2]==u[1]+1&&u=u[^1]);a}
%Y A299985 Cf. A299975 (analog with positive terms), A299957 (analog with digit 1), A299970, A299982..A299988, A299969 (digit 0, 2..8, 9).
%K A299985 nonn,base
%O A299985 0,2
%A A299985 _M. F. Hasler_ and _Eric Angelini_, Feb 22 2018