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 A147755 #14 Oct 30 2017 20:16:49
%S A147755 1,0,1,1,3,0,1,2,1,1,1,3,7,0,1,2,1,2,5,2,3,1,1,2,3,3,3,7,15,0,1,2,1,4,
%T A147755 2,2,3,2,2,10,5,2,5,3,7,1,1,2,3,2,5,6,3,3,3,3,3,7,7,15,31,0,1,2,1,4,2,
%U A147755 2,3,4,9,2,2,4,2,3,7,2,2,2,2,10,21,5,5,2,2,5,11,3,5,7,15,1,1,2,3,4,2,6,3,2
%N A147755 a(n) = the largest integer that, when represented in binary, occurs at least twice as a substring in the binary representation of n.
%C A147755 The substrings (each equal to the binary representation of a(n)) may overlap in the binary representation of n.
%H A147755 Alois P. Heinz, <a href="/A147755/b147755.txt">Table of n, a(n) for n = 3..8190</a>
%e A147755 21 in binary is 10101. 101 (5 in decimal) occurs twice in 10101: (101)01 and 10(101). Since no larger integer (when represented in binary) occurs more than once within 10101, then a(21) = 5.
%t A147755 Table[With[{d = IntegerDigits[n, 2]}, SelectFirst[Range[n, 0, -1], SequenceCount[d, IntegerDigits[#, 2], Overlaps -> True] >= 2 &]], {n, 3, 104}] (* _Michael De Vlieger_, Oct 30 2017 *)
%Y A147755 Cf. A147756, A242869.
%K A147755 base,nonn,look
%O A147755 3,5
%A A147755 _Leroy Quet_, Nov 11 2008
%E A147755 Extended by _Ray Chandler_, Nov 14 2008