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

Offset: 1

Author

Vladimir Shevelev and Peter J. C. Moses, Nov 02 2012

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Cf. A195270, A195271, A195377, A195325, A195329, A195379.

Programs

Mathematica

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

PARI

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