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Search: id:A061119
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OFFSET
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1,1
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COMMENT
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p and p^2 + 2^p are both prime only for p=3. All positive n satisfy the congruence n=3 (mod 6). - Lekraj Beedassy (lbeedassy(AT)hotmail.com), Sep 07 2004
For values of n, see A064539. - Lekraj Beedassy (blekraj(AT)yahoo.com), Jan 01 2007
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REFERENCES
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J.-M. De Koninck & A. Mercier, 1001 Problemes en Theorie Classique Des Nombres,Problem 165 pp. 30; 160, Ellipses Paris 2004.
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EXAMPLE
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a(3) = 593 = 2^9 +9^2. a(4) = 32993= 2^15 + 15^2.
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PROGRAM
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(PARI) for(n=1, 10^7, if(isprime(n^2+2^n), print(n^2+2^n)))
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CROSSREFS
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Cf. A001580.
Adjacent sequences: A061116 A061117 A061118 this_sequence A061120 A061121 A061122
Sequence in context: A009719 A128300 A001601 this_sequence A049985 A126579 A051710
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 21 2001
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EXTENSIONS
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More terms from Jason Earls (zevi_35711(AT)yahoo.com), Aug 09 2001. Next term too large to include.
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