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A193598 Even numbers k such that r(k) < r(k/2), where r(n) is the distance from n to the nearest prime. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 18 20:18 EDT 2019. Contains 328197 sequences. (Running on oeis4.)