A049716 a(n) = 2*n + 1 - prevprime(2*n + 1).

1, 2, 2, 2, 4, 2, 2, 4, 2, 2, 4, 2, 4, 6, 2, 2, 4, 6, 2, 4, 2, 2, 4, 2, 4, 6, 2, 4, 6, 2, 2, 4, 6, 2, 4, 2, 2, 4, 6, 2, 4, 2, 4, 6, 2, 4, 6, 8, 2, 4, 2, 2, 4, 2, 2, 4, 2, 4, 6, 8, 10, 12, 14, 2, 4, 2, 4, 6, 2, 2, 4, 6, 8, 10, 2, 2, 4, 6, 2, 4, 6, 2, 4, 2, 4, 6, 2, 4, 6, 2, 2, 4

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Examples

			n:     1  2  3  4  5  6  7  8 ...
2n+1:  3  5  7  9 11 13 15 17 ...
pp:    2  3  5  7  7 11 13 13 ...
diff:  1  2  2  2  4  2  2  4 ...
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A049613, A049653, A049711, A049847.

Programs

Maple

seq(2*n+1-prevprime(2*n+1), n=1..100); # Robert Israel, Jul 05 2018

Mathematica

Table[2n+1-NextPrime[2n+1,-1],{n,100}] (* Harvey P. Dale, Sep 21 2013 *)

PARI

a(n) = 2*n+1-precprime(2*n); \\ Michel Marcus, Jul 06 2018

Formula

a(n) = A049711(2*n+1). - R. J. Mathar, Oct 26 2015