

A240882


Numbers n such that n  4*k^2 is a prime for all k > 0 with k^2 < n/4.


0



6, 7, 9, 11, 15, 21, 23, 27, 33, 35, 47, 77, 83, 143, 167, 227, 437
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OFFSET

1,1


COMMENTS

No other terms with n < 1000000.  Colin Barker, Apr 14 2014


LINKS

Table of n, a(n) for n=1..17.


EXAMPLE

21 is in this sequence because 214*1^2 = 17 and 214*2^2 = 5 are both prime.


PROG

(PARI) isOK(n) = k=1; until(k^2>=n/4, if(!isprime(n4*k^2), return(0)); k++); 1;
for(n=3, 1000000, if(isOK(n), print1(n, ", "))) \\ Colin Barker, Apr 14 2014


CROSSREFS

Cf. A240842.
Sequence in context: A175221 A094010 A100348 * A241266 A095908 A094698
Adjacent sequences: A240879 A240880 A240881 * A240883 A240884 A240885


KEYWORD

nonn,more


AUTHOR

Ilya Lopatin and JuriStepan Gerasimov, Apr 14 2014


EXTENSIONS

One missing term and one additional term from Colin Barker, Apr 14 2014


STATUS

approved



