A162738 a(n) is the smallest positive multiple of {the n-th composite} that is greater than the n-th prime.

4, 6, 8, 9, 20, 24, 28, 30, 32, 36, 40, 42, 44, 48, 50, 78, 81, 84, 90, 96, 99, 102, 105, 108, 114, 117, 120, 126, 132, 135, 138, 144, 147, 150, 153, 156, 162, 165, 168, 228, 232, 240, 248, 252, 256, 260, 264, 272, 276, 280, 288, 296, 300, 304, 308, 312, 320, 324

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = ceiling(p(n)/c(n))*c(n), where c(n) is the n-th composite, and p(n) is the n-th prime.

Maple

A002808 := proc(n) option remember ; if n = 1 then 4; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) : fi; od: fi; end: A162738 := proc(n) A002808(n)*ceil( ithprime(n)/A002808(n)) ; end: seq(A162738(n), n=1..100) ; # R. J. Mathar, Jul 16 2009

Mathematica

prs=Prime[Range[60]]; comps=Rest[Complement[Range[Last[prs]+1], prs]]; Ceiling[First[#]/Last[#]]Last[#]&/@Thread[{prs, Take[comps, 60]}] (* Harvey P. Dale, Oct 02 2011 *)

Crossrefs

Sequence in context: A367176 A121719 A267509 * A366826 A161600 A032350

Adjacent sequences: A162735 A162736 A162737 * A162739 A162740 A162741

Keyword

nonn

Author

Leroy Quet, Jul 12 2009

Extensions

Extended beyond a(16) by R. J. Mathar, Jul 16 2009

Status

approved