A163400 Number of bits in binary expansion of n-th nonprime.

1, 1, 3, 3, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8

Offset: 1

Author

Juri-Stepan Gerasimov, Jul 26 2009

Keywords

• nonn
• easy
• base

Comments

Here n-th nonprime=A141468(n).

For n > 2, a(n) = A029837(n) or A029837(n)+1.

Examples

			a(1)=1(0=nonprime(1) written in base 2 and 10); a(2)=1(1=nonprime(2) written in base 2 and 10); a(3)=3(100=nonprime(3) written in base 2 where 4=nonprime(3) written in base 10).
		

Links

• J. Mulder, Table of n, a(n) for n = 1..90409

Crossrefs

Cf. A035100, A141468.

Programs

Maple

A141468 := proc(n) option remember; if n = 1 then 0; else for a from procname(n-1)+1 do if not isprime(a) then return a; fi; od: fi; end: A070939 := proc(n) max(1,ilog2(n)+1) ; end: A163400 := proc(n) A070939(A141468(n)) ; end: seq(A163400(n),n=1..120) ; # R. J. Mathar, Oct 10 2009

Mathematica

Prepend[Flatten@ Array[If[PrimeQ[ # ], {}, IntegerLength[ #, 2]] &, 100000], 1] (* Jasper Mulder (jasper.mulder(AT)planet.nl), Jun 03 2010 *)

Extensions

Edited by Charles R Greathouse IV, Mar 22 2010