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%I #18 Feb 13 2013 23:58:31
%S 29,71,137,197,239,269,347,419,431,641,659,809,821,1061,1091,1151,
%T 1289,1489,1607,1721,1783,1877,1949,1993,2083,2141,2267,2339,2381,
%U 2389,2549,2729,2801,2833,2969,2999,3019,3041,3217,3253,3299,3329,3389,3461
%N 4-gap primes: Prime p is a term iff there is no prime between 4*p and 4*nextprime(p), where nextprime=A151800.
%H M. F. Hasler, <a href="/A218561/b218561.txt">Table of n, a(n) for n = 1..4911</a> (all terms up to 5*10^5).
%e 29 is in the sequence since there are no primes in the interval(4*29,4*31)=(116,124)
%t Select[Prime[Range[500]],Count[Range[4*#,4*NextPrime[#]],_?PrimeQ]==0&] (* _Harvey P. Dale_, Jan 05 2013 *)
%o (PARI) is_A218561(p)=isprime(p)&nextprime(4*p)>=4*nextprime(p+1) \\ - _M. F. Hasler_, Nov 03 2012
%Y Cf. A195270, A195271, A195377, A195325, A195329, A195379.
%K nonn
%O 1,1
%A _Vladimir Shevelev_ and _Peter J. C. Moses_, Nov 02 2012
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