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A023281
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Numbers n such that n remains prime through 3 iterations of function f(x) = 4x + 3.
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2, 109, 179, 571, 677, 977, 1279, 1447, 1747, 1901, 2207, 2671, 3119, 3917, 5011, 5399, 5441, 5569, 5791, 6211, 6607, 7079, 7417, 8369, 8831, 9221, 9697, 9769, 11821, 11897, 12347, 13537, 13669, 13691, 13729, 13781, 13907, 14747, 14851, 15581, 17231, 17497
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| n, 4*n+3, 16*n+15 and 64*n+63 are primes. [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 04 2010]
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MAPLE
| f:=proc(x) options operator, arrow: 4*x+3 end proc: a:=proc(n) if isprime(n)= true and isprime(f(n))=true and isprime(f(f(n)))=true and isprime(f(f(f(n)))) =true then n else end if end proc: seq(a(n), n=1..20000); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 01 2008
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PROG
| (MAGMA) [n: n in [1..150000] | IsPrime(n) and IsPrime(4*n+3) and IsPrime(16*n+15) and IsPrime(64*n+63)] [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 04 2010]
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CROSSREFS
| Sequence in context: A156502 A111456 A157067 * A042457 A062656 A173372
Adjacent sequences: A023278 A023279 A023280 * A023282 A023283 A023284
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KEYWORD
| nonn
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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