A163400 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

COMMENTS

Here n-th nonprime=A141468(n).

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

LINKS

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

EXAMPLE

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).

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 *)

CROSSREFS

Cf. A035100, A141468.

Sequence in context: A298199 A282623 A090589 * A090972 A318241 A181742

Adjacent sequences: A163397 A163398 A163399 * A163401 A163402 A163403

KEYWORD

nonn,easy,base

AUTHOR

Juri-Stepan Gerasimov, Jul 26 2009

EXTENSIONS

Edited by Charles R Greathouse IV, Mar 22 2010

STATUS

approved