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 A299976 #4 Feb 23 2018 09:49:54
%S A299976 1,5,11,15,21,25,31,29,7,9,17,19,27,33,3,13,23,37,24,2,4,12,14,22,34,
%T A299976 26,10,6,20,16,30,32,28,8,18,38,48,58,68,78,82,44,42,54,52,64,62,74,
%U A299976 72,84,76,40,36,50,46,60,56,70,66,80,81,35,41,45,51,55,61,65,71,75,85,77,39,47,49,57,59,67,69,87,73,43,53,63,83,79,86,90,96,100
%N A299976 Lexicographic first sequence of positive integers such that a(n) + a(n+1) has a digit 6, and no term occurs twice.
%C A299976 A permutation of the positive integers.
%o A299976 (PARI) a(n,f=1,d=6,a=1,u=[a])={for(n=2,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 A299976 Cf. A299986 (analog with nonnegative terms), A299957 (analog with digit 1), A299971, A299972, ..., A299979 (digit 0, 2, ..., 9).
%K A299976 nonn,base
%O A299976 1,2
%A A299976 _M. F. Hasler_ and _Eric Angelini_, Feb 22 2018