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Search: id:A116214
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| A116214 |
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Numbers n such that both n*(n+2)-(n+1) and n*(n+2)+(n+1) are primes. |
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2
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| 2, 3, 4, 5, 8, 9, 10, 15, 19, 20, 30, 38, 44, 45, 53, 54, 55, 59, 64, 65, 85, 93, 100, 114, 125, 130, 140, 144, 148, 153, 154, 158, 159, 163, 180, 195, 218, 219, 230, 240, 258, 263, 264, 305, 330, 349, 350, 360, 373, 385, 395, 418, 419, 448, 449, 455, 473, 474
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Sequence a(k)*(a(k)+2) = 8, 15, 24, 35, 80, 99, ... equals A069826.
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EXAMPLE
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20*22 = 440; both 440-21 = 419 and 440+21 = 461 are prime, hence 20 is a term.
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PROGRAM
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(MAGMA) [ n: n in [1..500] | IsPrime(n*(n+2)+(n+1)) and IsPrime(n*(n+2)-(n+1)) ]; /* Klaus Brockhaus, Apr 17 2007 */
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CROSSREFS
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Cf. A005563 (n(n+2)), A069826 (numbers n such that sigma(n^2-n-1) = n*(n+1)).
Sequence in context: A094566 A087278 A054219 this_sequence A044051 A083132 A118956
Adjacent sequences: A116211 A116212 A116213 this_sequence A116215 A116216 A116217
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KEYWORD
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nonn
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AUTHOR
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J. M. Bergot (thekingfishb(AT)yahoo.ca), Apr 16 2007
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EXTENSIONS
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Edited and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Apr 17 2007
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