A033921 Largest proper substring of 2^n that is a power of 2 (0 if none).

0, 0, 0, 0, 1, 2, 4, 8, 2, 2, 4, 8, 4, 8, 16, 32, 0, 2, 4, 8, 8, 2, 4, 8, 16, 32, 64, 8, 8, 8, 8, 64, 4, 8, 8, 8, 8, 8, 8, 8, 16, 32, 8, 8, 16, 32, 64, 32, 8, 4, 8, 8, 4, 4, 8, 8, 4, 8, 8, 64, 8, 8, 16, 8, 16, 32, 64, 64, 8, 8, 16, 32, 64, 32, 8, 16, 32, 64, 4, 8, 8, 16, 32, 64, 16, 32, 64, 8, 8

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• base

Examples

			2^15={32}768, so a(15)=32.
		

Links

• Robert Israel, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A000079.

Programs

Maple

for n from 0 to 100 do
L[n]:= sprintf("%d",2^n);
A[n]:= 0;
for k from n-1 by -1 to 0 do
  if StringTools[Search](L[k],L[n]) <> 0 then
    A[n]:= 2^k; break
  fi
od
od:
seq(A[n],n=0..100); # Robert Israel, Aug 16 2018

Extensions

More terms from Patrick De Geest, Jun 15 1998