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A116886
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Primes p that remain prime through at least 2 iterations of function f(p)=p^2+4.
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4
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3, 17, 103, 137, 277, 313, 677, 743, 1117, 1627, 2003, 2143, 3407, 3677, 4483, 5087, 5903, 7177, 7333, 8087, 8093, 8147, 8537, 8573, 9293, 9473, 10177, 10477, 11173, 13807, 14897, 15107, 16657, 19753, 21563, 22307, 24113, 26113, 26417, 26633
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Numbers p with property that p, q=p^2+4, and r=q^2+4 are all prime. - Zak Seidov (zakseidov(AT)yahoo.com), Sep 08 2009
a(n)=sqrt(A165218(n)-4). - Zak Seidov (zakseidov(AT)yahoo.com), Sep 08 2009
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EXAMPLE
| 17 is prime, 17^2+4=293 is prime and 293^2+4=85853 is prime.
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MATHEMATICA
| Select[Prime[Range[2*7! ]], PrimeQ[ #^2+4]&&PrimeQ[(#^2+4)^2+4]&] [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Feb 26 2010]
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CROSSREFS
| Cf. A062324, A116887, A116888, A116889.
A045637, A062324, A165218.
Sequence in context: A161940 A074565 A054365 * A163064 A020069 A020024
Adjacent sequences: A116883 A116884 A116885 * A116887 A116888 A116889
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KEYWORD
| nonn
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AUTHOR
| Giovanni Resta (g.resta(AT)iit.cnr.it), Feb 27 2006
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EXTENSIONS
| Edited by N. J. A. Sloane, Sep 18 2009 at the suggestion of R. J. Mathar
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