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Search: id:A063760
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| A063760 |
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Sum of non-unitary divisors of n is a prime and sets a new record for such primes. |
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+0
1
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| 4, 9, 25, 36, 144, 441, 676, 1089, 1296, 1764, 2304, 4900, 5184, 9216, 15876, 33124, 36100, 43264, 51984, 82944, 115600, 142884, 147456, 224676, 266256, 298116, 331776, 389376, 467856
(list; graph; listen)
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OFFSET
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0,1
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EXAMPLE
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sigma(441) - usigma(441) = 241, a prime.
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PROGRAM
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(PARI) u(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d)); a=0; for(n=1, 50000, x=sigma(n)-u(n); if(isprime(x), b=x; if(b>a, a=b; print(n))))
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CROSSREFS
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Cf. A048146.
Sequence in context: A063577 A087058 A046659 this_sequence A130448 A046451 A082200
Adjacent sequences: A063757 A063758 A063759 this_sequence A063761 A063762 A063763
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KEYWORD
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nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Aug 24 2001
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