A218561 - OEIS

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A218561

4-gap primes: Prime p is a term iff there is no prime between 4*p and 4*nextprime(p), where nextprime=A151800.

29, 71, 137, 197, 239, 269, 347, 419, 431, 641, 659, 809, 821, 1061, 1091, 1151, 1289, 1489, 1607, 1721, 1783, 1877, 1949, 1993, 2083, 2141, 2267, 2339, 2381, 2389, 2549, 2729, 2801, 2833, 2969, 2999, 3019, 3041, 3217, 3253, 3299, 3329, 3389, 3461

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

M. F. Hasler, Table of n, a(n) for n = 1..4911 (all terms up to 5*10^5).

EXAMPLE

29 is in the sequence since there are no primes in the interval(4*29,4*31)=(116,124)

MATHEMATICA

Select[Prime[Range[500]], Count[Range[4*#, 4*NextPrime[#]], _?PrimeQ]==0&] (* Harvey P. Dale, Jan 05 2013 *)

PROG

(PARI) is_A218561(p)=isprime(p)&nextprime(4*p)>=4*nextprime(p+1) \\ - M. F. Hasler, Nov 03 2012

CROSSREFS