A064891 "Binary potency" of n: length of shortest blocks of 0's inserted between the bits of n required to "dilute" it into a nonprime.

0, 1, 2, 0, 2, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 2, 0, 1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 3, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 3, 0, 0, 0, 3, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 1, 0, 3, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0

Offset: 1

Author

Marc LeBrun, Oct 10 2001

Keywords

• base
• easy
• nonn

Comments

Zero for all nonprime n. Note that the +2 dilution of 3 is not the +1 dilution of 5!

Examples

			3 = 11 -> 0101 = 5 -> 001001 = 9, so a(3) = 2; 5 = 101 -> 010001 = 17 -> 001000001 = 65, so a(5) = 2
		

Crossrefs

Cf. A000040, A064892, A064893.