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 A031045 #28 Sep 12 2019 04:48:11
%S A031045 0,1,2,3,4,5,6,7,0,1,1,1,2,1,3,1,4,1,5,1,6,1,7,1,0,2,1,2,2,2,3,2,4,2,
%T A031045 5,2,6,2,7,2,0,3,1,3,2,3,3,3,4,3,5,3,6,3,7,3,0,4,1,4,2,4,3,4,4,4,5,4,
%U A031045 6,4,7,4,0,5,1,5,2,5,3,5,4,5,5,5,6,5,7,5,0,6,1
%N A031045 Triangle T(n,k): write n in base 8, reverse order of digits.
%H A031045 Robert Israel, <a href="/A031045/b031045.txt">Table of n, a(n) for n = 0..10003</a> (rows 0 to 3646, flattened)
%p A031045 seq(op(convert(n,base,8)),n=0..100); # _Robert Israel_, Jul 22 2019
%t A031045 Flatten[Table[Reverse[IntegerDigits[n,8]],{n,80}]] (* _Harvey P. Dale_, Aug 08 2011 *)
%o A031045 (PARI) A031045(n, k=-1)=/*k<0&&error("Flattened sequence not yet implemented.");*/n\8^k%8 \\ Assuming that columns are numbered starting with k=0 as in A030308, A030341, ... Note: The operation could be done using bitwise arithmetic, bitand(n>>(3*k),7), but this is not significantly faster in PARI. - _M. F. Hasler_, Jul 21 2013
%Y A031045 Cf. A030308, A030341, A030386, A031235, A030567, A031007, A031087, A031298 for the base-2 to base-10 analogs.
%K A031045 nonn,base,tabf,less
%O A031045 0,3
%A A031045 _Clark Kimberling_
%E A031045 Initial 0 and better name by _Philippe Deléham_, Oct 20 2011