A074766 a(n) = prime(2n) - 2*prime(n) - n.

-2, -1, 0, 1, 2, 5, 2, 7, 6, 3, 6, 3, 6, 7, 4, 9, 4, 11, 10, 11, 14, 13, 10, 21, 10, 11, 18, 21, 24, 25, 8, 17, 10, 25, 16, 21, 22, 19, 24, 23, 22, 29, 18, 27, 24, 35, 22, 9, 18, 33, 40, 39, 42, 37, 32, 31, 24, 41, 34, 37, 46, 35, 24, 33, 42, 43, 28, 27, 24, 41, 44, 37, 32, 37, 30, 39, 32

Offset: 1

Author

Werner D. Sand, Sep 29 2002

Keywords

• sign

Comments

Conjecture: p(2n) - 2p(n) < 2n for all n.

Examples

			a(9) = p(18) - 2p(9) - 9 = 61 - 2*23 - 9 = 6.
		

Crossrefs

Cf. A066066.

Programs

Maple

A074766:=n->ithprime(2*n)-2*ithprime(n)-n: seq(A074766(n), n=1..100); # Wesley Ivan Hurt, Jan 16 2017

Mathematica

Table[Prime[2 n] - 2 Prime[n] - n, {n, 80}] (* Harvey P. Dale, Mar 04 2017 *)

Formula

a(n) = A066066(n) - n.