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Search: id:A064271
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| A064271 |
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Numbers n such that sigma(n)-2n is prime. |
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+0
1
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| 18, 20, 36, 100, 104, 196, 324, 392, 464, 576, 650, 784, 800, 900, 968, 1352, 1936, 1952, 2450, 2500, 3136, 4356, 4624, 5184, 6050, 6400, 9216, 10000, 10404, 10816, 12800, 13456, 14400, 15376, 15488, 16928, 18496, 20000, 20736, 23104, 26912
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,1000
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EXAMPLE
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n=100: sigma(100)-2*100 = 17.
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PROGRAM
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(PARI) j=[]; for(n=1, 50000, x=sigma(n)-2*n; if(x>0 && isprime(x), j=concat(j, n))); j
(PARI) { n=0; for (m=1, 10^9, if (isprime(sigma(m) - 2*m), write("b064271.txt", n++, " ", m); if (n==1000, break)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Sep 11 2009]
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CROSSREFS
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Sequence in context: A054279 A164711 A036170 this_sequence A113541 A113542 A075865
Adjacent sequences: A064268 A064269 A064270 this_sequence A064272 A064273 A064274
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KEYWORD
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easy,nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Sep 23 2001
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