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 A146091 #5 Dec 09 2018 12:57:26
%S A146091 1,10,19,82,91,100,163,172,181,730,739,748,811,820,829,892,901,910,
%T A146091 1459,1468,1477,1540,1549,1558,1621,1630,1639,6562,6571,6580,6643,
%U A146091 6652,6661,6724,6733,6742,7291,7300,7309,7372,7381,7390,7453,7462,7471,8020,8029,8038,8101,8110,8119
%N A146091 a(n) = 3*A146085(n) - 2.
%C A146091 Positive integers such that for every integer m==4 (mod 9) there exists a unique representation of m as a sum of the form a(l)+3a(s).
%o A146091 (PARI) isa(n) = {my(d=Vecrev(digits(n, 3)), k=3); while (k <= #d, if (d[k], return (0)); k += 2;); d[1] == 1;} \\ A146085
%o A146091 isok(n) = !((n+2) % 3) && isa((n+2)/3); \\ _Michel Marcus_, Dec 09 2018
%Y A146091 Cf. A146085, A146087, A145812, A145818.
%K A146091 nonn
%O A146091 1,2
%A A146091 _Vladimir Shevelev_, Oct 27 2008
%E A146091 More terms from _Michel Marcus_, Dec 09 2018