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 A364885 #9 Aug 26 2023 08:57:09 %S A364885 0,1,3,2,5,7,4,9,11,6,8,17,19,10,13,16,33,35,18,21,15,32,65,67,34,37, %T A364885 23,12,64,129,131,66,69,39,20,25,128,257,259,130,133,71,36,41,27,256, %U A364885 513,515,258,261,135,68,73,43,14,512,1025,1027,514,517,263,132,137,75,22,24 %N A364885 Triangle T(n, k), n >= 0, k = 0..n, read by rows; T(0, 0) = 0, and for any n > 0, k = 0..n, T(n, k) is the least number obtained by turning a 0 into a 1 in the binary expansion of the k-th term of the (0-based) flattened sequence. %C A364885 In other words, T(n, k) = a(k) OR 2^e for some e >= 0 (where OR denotes the bitwise OR operator). %C A364885 As a flat sequence, this is a permutation of the nonnegative integers (as, for any h >= 0, the sequence contains all numbers with Hamming weight h); see A365080 for the inverse. %H A364885 Rémy Sigrist, <a href="/A364885/a364885.gp.txt">PARI program</a> %H A364885 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A364885 T(n, 0) = 2^(n-1) for any n > 0. %F A364885 A000120(a(n)) = A057945(n). %e A364885 Triangle begins: %e A364885 0 %e A364885 1, 3 %e A364885 2, 5, 7 %e A364885 4, 9, 11, 6 %e A364885 8, 17, 19, 10, 13 %e A364885 16, 33, 35, 18, 21, 15 %e A364885 32, 65, 67, 34, 37, 23, 12 %e A364885 64, 129, 131, 66, 69, 39, 20, 25 %e A364885 128, 257, 259, 130, 133, 71, 36, 41, 27 %e A364885 256, 513, 515, 258, 261, 135, 68, 73, 43, 14 %e A364885 512, 1025, 1027, 514, 517, 263, 132, 137, 75, 22, 24 %e A364885 ... %o A364885 (PARI) See Links section. %Y A364885 See A364884 for a similar sequence. %Y A364885 Cf. A000120, A057945, A365080 (inverse). %K A364885 nonn,base,tabl %O A364885 0,3 %A A364885 _Rémy Sigrist_, Aug 12 2023