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 A187786 #12 Jan 29 2014 04:03:43
%S A187786 0,1,2,3,4,5,6,5,6,7,8,9,10,12,9,10,12,11,13,14,9,10,12,11,13,14,11,
%T A187786 13,14,15,16,17,18,20,24,17,18,20,24,19,21,22,25,26,28,17,18,20,24,19,
%U A187786 21,22,25,26,28,19,21,22,25,26,28,23,27,29,30,17,18,20
%N A187786 Table read by rows, where n-th row contains all numbers having in binary representation as many zeros and ones as n.
%C A187786 For k = 0..A090706(n)-1: A023416(T(n,k))=A023416(n); A000120(T(n,k))=A000120(n); A053644(n)<=T(n,k)<=A003817(n);
%C A187786 T(n,k) = n for some k;
%C A187786 A187769 contains all rows without repetitions.
%H A187786 Reinhard Zumkeller, <a href="/A187786/b187786.txt">Rows n = 0..255 of triangle, flattened</a>
%H A187786 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>
%e A187786 . n n-th row binary row length
%e A187786 . -- --------------------- ------------------------------- ----------
%e A187786 . 0 {0} {0} 1
%e A187786 . 1 {1} {1} 1
%e A187786 . 2 {2} {10} 1
%e A187786 . 3 {3} {11} 1
%e A187786 . 4 {4} {100} 1
%e A187786 . 5 {5,6} {101,110} 2
%e A187786 . 6 {5,6} {101,110} 2
%e A187786 . 7 {7} {111} 1
%e A187786 . 8 {8} {1000} 1
%e A187786 . 9 {9,10,12} {1001,1010,1100} 3
%e A187786 . 10 {9,10,12} {1001,1010,1100} 3
%e A187786 . 11 {11,13,14} {1011,1101,1110} 3
%e A187786 . 12 {9,10,12} {1001,1010,1100} 3
%e A187786 . 13 {11,13,14} {1011,1101,1110} 3
%e A187786 . 14 {11,13,14} {1011,1101,1110} 3
%e A187786 . 15 {15} {1111} 1
%e A187786 . 16 {16} {10000} 1
%e A187786 . 17 {17,18,20,24} {10001,10010,10100,11000} 4
%e A187786 . 18 {17,18,20,24} {10001,10010,10100,11000} 4
%e A187786 . 19 {19,21,22,25,26,28} {10011,10101,10110,11001,11010,11100} 6
%e A187786 . 20 {17,18,20,24} {10001,10010,10100,11000} 4 .
%o A187786 (Haskell)
%o A187786 import List (find)
%o A187786 import Maybe (fromJust)
%o A187786 a187786 n k = a187786_tabf !! n !! k
%o A187786 a187786_row n = fromJust $ find (elem n) a187769_tabf
%o A187786 a187786_tabf = map a187786_row [0..]
%K A187786 nonn,base,tabf,look
%O A187786 0,3
%A A187786 _Reinhard Zumkeller_, Jan 06 2013