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A059456
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Unsafe primes: primes not in A005385.
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15
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2, 3, 13, 17, 19, 29, 31, 37, 41, 43, 53, 61, 67, 71, 73, 79, 89, 97, 101, 103, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 173, 181, 191, 193, 197, 199, 211, 223, 229, 233, 239, 241, 251, 257, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| A010051(a(n))*(1-A156659(a(n))) = 1; subsequence of A156657. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 18 2009]
Also, primes p such that p-1 is a non-semiprime. [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Apr 28 2010]
Conjecture: From the sequence of prime numbers, let 2 and remove the first data iteration of 2*p+1; leave 3 and remove the prime data by the iteration 2*p+1 and we get the sequence. Example for p=2, remove(5,11,23,47); p=3, remove(7); p=13, p=17, p=19, p=23, remove(47); and so on. [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 07 2010]
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EXAMPLE
| 31 is here because (31-1)/2=15 is not prime. 2 and 3 are here because 1/2 and 1 are not prime numbers.
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CROSSREFS
| A005384, A005385, A053176, A059452-A059456, A007700, A005602, A023272, A023302, A023330.
Sequence in context: A101541 A059670 A038975 * A019394 A048704 A045340
Adjacent sequences: A059453 A059454 A059455 * A059457 A059458 A059459
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Feb 02 2001
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