A014683 - OEIS

A014683

In the sequence of positive integers add 1 to each prime number.

1, 3, 4, 4, 6, 6, 8, 8, 9, 10, 12, 12, 14, 14, 15, 16, 18, 18, 20, 20, 21, 22, 24, 24, 25, 26, 27, 28, 30, 30, 32, 32, 33, 34, 35, 36, 38, 38, 39, 40, 42, 42, 44, 44, 45, 46, 48, 48, 49, 50, 51, 52, 54, 54, 55, 56, 57, 58, 60, 60, 62, 62, 63, 64, 65, 66, 68, 68, 69, 70, 72, 72

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OFFSET

1,2

COMMENTS

For n >= 3, a(n) = smallest composite number m such that m - (n-2) is a prime. - Amarnath Murthy and Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Mar 08 2003

LINKS

N. J. A. Sloane, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = n + pi(n) - pi(n-1). - Wesley Ivan Hurt, Jun 15 2013

a(n) = n + A010051(n). - Reinhard Zumkeller, Nov 01 2014

MATHEMATICA

Array[If[PrimeQ[#], #+1, #]&, 80] (* Harvey P. Dale, Jul 21 2013 *)

PROG

(PARI) a(n)=n+isprime(n)

(Haskell)

a014683 n = n + a010051' n -- Reinhard Zumkeller, Nov 01 2014

(Python)