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 A334919 #52 Sep 08 2022 08:46:25
%S A334919 5,8,9,13,16,17,18,21,23,25,28,29,30,33,37,38,40,41,43,44,45,48,49,51,
%T A334919 53,56,57,58,61,62,63,65,68,69,72,73,77,78,79,81,82,83,84,85,86,88,89,
%U A334919 93,95,96,97,98,100,101,103,105,106,107,108,109,113,114,117
%N A334919 Numbers of the form i + j + 3*i*j for i,j >= 1 together with numbers of the form -i - j + 3*i*j for i,j >= 2.
%e A334919 5 is a term because 5 = 1+1+3*1*1.
%e A334919 8 is a term because 8 = -2-2+3*2*2.
%e A334919 16 is a term because 16 = 2+2+3*2*2.
%o A334919 (Magma) [m:m in [1..101]|exists(a){i:i in [1..m-1]|IsIntegral((m-i)/(1+3*i))} or exists(b){j:j in [2..m-1]|IsIntegral((m+j)/(-1+3*j)) and (m+j)/(-1+3*j) ge 2}]; // _Marius A. Burtea_, Jun 04 2020
%Y A334919 Complement of A335031.
%K A334919 nonn
%O A334919 1,1
%A A334919 _Davide Rotondo_, May 16 2020