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Search: id:A092120
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| A092120 |
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a(n) is the first term in a sequence of primes such that a(n)+4m^2 is also prime for m = 1 to n, but composite for m = n+1. |
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+0
1
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| 19, 3, 277, 43, 53593, 7, 67, 37, 1483087, 1867783, 9671300983, 376040154163, 13491637509487, 604490757900187, 409333
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Similar to A092474 except that a(n)+4m^2 is composite for m = n+1.
a(19)=163. All other terms after a(15) are above 10^17 (if they exist). [From Jens Kruse Andersen (jens.k.a(AT)get2net.dk), Oct 24 2008]
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LINKS
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Carlos Rivera, Puzzle 464. p+4*x^2. [From Jens Kruse Andersen (jens.k.a(AT)get2net.dk), Oct 24 2008]
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EXAMPLE
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a(4) = 43: 43+4*1^2 = 47, which is prime. 43+4*2^2 = 59, which is prime. 43+4*3^2 = 79, which is prime. 43+4*4^2 = 107, which is prime. 43+4*5^2 = 143 = 11*13, which is composite.
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CROSSREFS
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Sequence in context: A040352 A040353 A128160 this_sequence A002206 A040349 A040350
Adjacent sequences: A092117 A092118 A092119 this_sequence A092121 A092122 A092123
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KEYWORD
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nonn
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AUTHOR
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Ray G. Opao (1260(AT)email.com), Mar 29 2004
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EXTENSIONS
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Correction and a(11) - a(15) from Jens Kruse Andersen (jens.k.a(AT)get2net.dk), Oct 24 2008
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