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Search: id:A130038
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| A130038 |
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Even numbers n such that n-7 is prime, but neither n-3 nor n-5 is prime. |
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| 30, 38, 54, 60, 68, 80, 90, 96, 120, 138, 146, 158, 164, 174, 180, 188, 206, 218, 240, 248, 258, 264, 270, 278, 290, 300, 324, 338, 344, 360, 366, 374, 380, 390, 396, 408, 416, 428, 440, 450, 456, 474, 486, 498, 510, 516, 530, 548, 554, 564, 570, 578, 584
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Even numbers that are the sum of 7 and another prime number, but not the sum of 3 or 5 plus another prime.
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EXAMPLE
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30-7 is prime but 30-3 and 30-5 are not. Therefore 30 is in the sequence.
90-7 = 83 is prime, but neither 90-3 = 87 nor 90-5= 85 is prime, hence 90 is a term.
88-7 = 81 is not prime, hence 88 is not in the sequence.
86-7 = 79 is prime, and 86-3 = 83 is also prime, hence 86 is not in the sequence.
78-7 = 71 is prime, and 78-5 = 73 is also prime, hence 78 is not in the sequence.
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MATHEMATICA
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Select[2*Range[4, 500], PrimeQ[ # - 7] && ! PrimeQ[ # - 3] && ! PrimeQ[ # - 5] &] - Stefan Steinerberger
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PROGRAM
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(PARI) {forstep(n=2, 584, 2, if(isprime(n-7)&&!isprime(n-3)&&!isprime(n-5), print1(n, ", ")))} /* Klaus Brockhaus, Jul 25 2007 */
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CROSSREFS
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Adjacent sequences: A130035 A130036 A130037 this_sequence A130039 A130040 A130041
Sequence in context: A114840 A109426 A051657 this_sequence A001995 A004433 A025376
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KEYWORD
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nonn
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AUTHOR
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Anthony W Lawson (anthonylawson67(AT)optusnet.com.au), Jul 24 2007
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EXTENSIONS
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Edited, corrected and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jul 24 2007
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