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 A228146 #10 Sep 08 2022 08:46:05
%S A228146 -3,-5,-1,-9,-5,-3,-17,-3,-5,-1,-33,-17,-9,-1,-3,-65,-11,-17,-3,-5,-1,
%T A228146 -129,-65,-33,-17,-9,-5,-3,-257,-43,-65,-11,-17,-1,-5,-1,-513,-257,
%U A228146 -129,-13,-33,-17,-9,-1,-3,-1025,-171,-257,-43,-65,-11,-17,-3,-5,-1
%N A228146 Triangle T(n,k), read by rows: T(n,k) is the numerator of (1+2^(n-k+1))/(1-2^(k+1)).
%C A228146 The denominators are given in A228147.
%H A228146 Vincenzo Librandi, <a href="/A228146/b228146.txt">Rows n = 0..90, flattened</a>
%e A228146 Triangle begins:
%e A228146 -3;
%e A228146 -5, -1;
%e A228146 -9, -5, -3;
%e A228146 -17, -3, -5, -1;
%e A228146 -33, -17, -9, -1, -3;
%e A228146 -65, -11, -17, -3, -5, -1;
%e A228146 -129, -65, -33, -17, -9, -5, -3;
%e A228146 -257, -43, -65, -11, -17, -1, -5, -1;
%e A228146 -513, -257, -129, -13, -33, -17, -9, -1, -3;
%e A228146 -1025, -171, -257, -43, -65, -11, -17, -3, -5, -1; etc.
%t A228146 a[n_, k_] := Numerator[(1 + 2^(n - k + 1))/(1 - 2^(k + 1))]; Table[a[n, k], {n, 0, 10}, {k, 0, n}] // Flatten
%o A228146 (Magma) [Numerator((1+2^(n-k+1))/(1-2^(k+1))): k in [0..n], n in [0..10]];
%Y A228146 Cf. A228147.
%K A228146 sign,tabl
%O A228146 0,1
%A A228146 _Vincenzo Librandi_, Aug 15 2013