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 A087737 #17 May 20 2017 19:50:56
%S A087737 6,11,28,37,46,55,120,137,154,171,188,205,222,239,496,529,562,595,628,
%T A087737 661,694,727,760,793,826,859,892,925,958,991,2016,2081,2146,2211,2276,
%U A087737 2341,2406,2471,2536,2601,2666,2731,2796,2861,2926,2991,3056,3121
%N A087737 Value of (n,n+1) concatenated in binary representation.
%C A087737 a(n) = n * 2^A070939(n+1) + (n+1).
%H A087737 Paolo P. Lava, <a href="/A087737/b087737.txt">Table of n, a(n) for n = 1..10000</a>
%e A087737 n=12: 12->'1100', 12+1->'1101', a(12)='1100''1101'='11001101'->205.
%p A087737 a:= n-> n*(2^(ilog2(n+1)+1)+1)+1:
%p A087737 seq(a(n), n=1..50); # _Alois P. Heinz_, May 20 2017
%t A087737 Table[FromDigits[Join[IntegerDigits[n,2],IntegerDigits[n+1,2]],2],{n,50}] (* _Harvey P. Dale_, Jan 14 2013 *)
%t A087737 Table[n 2^IntegerLength[#, 2] + # &[n + 1], {n, 48}] (* _Michael De Vlieger_, May 20 2017 *)
%o A087737 (PARI) a(n) = fromdigits(Vec(concat(binary(n), binary(n+1))), 2); \\ _Michel Marcus_, May 20 2017
%Y A087737 Cf. A007088, A001704.
%K A087737 nonn,base
%O A087737 1,1
%A A087737 _Reinhard Zumkeller_, Oct 01 2003