A193598 Even numbers k such that r(k) < r(k/2), where r(n) is the distance from n to the nearest prime.

2, 18, 30, 42, 52, 54, 66, 68, 70, 78, 90, 98, 100, 102, 110, 112, 114, 126, 128, 130, 138, 150, 152, 162, 172, 174, 182, 190, 198, 210, 222, 230, 232, 234, 236, 238, 240, 242, 244, 250, 258, 268, 270, 282, 284, 286, 290, 292, 294, 306, 308

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

18 is in the sequence, since r(18) = 1 < 2 = r(9); 22 is not in the sequence, since r(22) = 1 >= 0 = r(11).

Prog

(PARI) r(n)=min(nextprime(n)-n, n-precprime(n))
forstep(k=2, 1e3, 2, if(r(k)<r(k/2), print1(k", "))) \\ Charles R Greathouse IV, Jul 31 2011

Crossrefs

r(n) is A051699.

Sequence in context: A098561 A141426 A101844 * A190047 A166259 A073213

Adjacent sequences: A193595 A193596 A193597 * A193599 A193600 A193601

Keyword

nonn

Author

Vladimir Shevelev, Jul 31 2011

Status

approved