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.
f:= proc(n) local L,m;
if n::odd then return true fi;
L:= convert(n,base,2);
for m from 2 to nops(L)-1 do
if L[1..m] = L[-m..-1] then return true fi;
od:
false
end proc:
select(f, [$2..101]); # Robert Israel, Feb 05 2016
a(91) = 11 because 91 = (1011)011_2 = 101(1011)_2 and 11 = 1011_2. a(84) = 0 because 84 = 1010100_2, only the empty bitstring is a proper prefix and suffix.
a:= proc(n) local m; m:=n;
while m>1 do m:= iquo(m, 2);
if m=irem(n, 2^(1+ilog2(m))) then return m fi
od; 0
end:
seq(a(n), n=0..100);
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