A033558 a(n) = 2n - {smallest prime > n}.

0, 1, 1, 3, 3, 5, 3, 5, 7, 9, 9, 11, 9, 11, 13, 15, 15, 17, 15, 17, 19, 21, 17, 19, 21, 23, 25, 27, 27, 29, 25, 27, 29, 31, 33, 35, 33, 35, 37, 39, 39, 41, 39, 41, 43, 45, 41, 43, 45, 47, 49, 51, 47, 49, 51, 53, 55, 57

Offset

1,4

Comments

By Bertrand's postulate, for n>3 a(n)>2. - Zak Seidov, Mar 06 2015

Links

Zak Seidov, Table of n, a(n) for n = 1..1000

Wikipedia, Bertrand's postulate

Maple

f := n->2*n-nextprime(n); [ seq(f(i), i=1..60) ];

Mathematica

Table[2*n-NextPrime[n], {n, 60}] (* Harvey P. Dale, Jul 23 2018 *)

Prog

(PARI) vector(60, n, 2*n - nextprime(n + 1)) \\ Zak Seidov, Mar 06 2015

Crossrefs

Cf. A151800 (least prime > n).

Sequence in context: A078587 A335074 A239931 * A046217 A057662 A015971

Adjacent sequences: A033555 A033556 A033557 * A033559 A033560 A033561

Keyword

nonn

Author

N. J. A. Sloane.

Status

approved