A163405 - OEIS

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A163405

a(n) = (n-th nonprime) + (number of bits in binary expansion of n-th nonprime).

1, 2, 7, 9, 12, 13, 14, 16, 18, 19, 21, 23, 25, 26, 27, 29, 30, 31, 32, 33, 35, 38, 39, 40, 41, 42, 44, 45, 46, 48, 50, 51, 52, 54, 55, 56, 57, 58, 60, 61, 62, 63, 64, 66, 68, 69, 71, 72, 73, 75, 76, 77, 79, 81, 82, 83, 84, 85, 87, 88, 89, 91, 92, 93, 94, 95, 97, 98, 99, 100, 101

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

OFFSET

1,2

COMMENTS

Here n-th nonprime = A141468(n) and n-th number of bits in binary expansion of n-th nonprime = A163400(n).

LINKS

Table of n, a(n) for n=1..71.

FORMULA

a(n) ~ n. [Charles R Greathouse IV, Dec 21 2011]

EXAMPLE

a(1) = 1 (= 0+1);

a(2) = 2 (= 1+1);

a(3) = 7 (= 4+3).

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: A163405 := proc(n) A141468(n)+A163400(n) ; end: seq(A163405(n), n=1..120) ; # R. J. Mathar, Oct 10 2009

CROSSREFS

Cf. A141468, A163400.

Sequence in context: A277737 A082371 A090348 * A049638 A190490 A059649

Adjacent sequences: A163402 A163403 A163404 * A163406 A163407 A163408

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Jul 26 2009

STATUS

approved