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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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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, 898704, 944784, 1016064, 1587600, 2286144, 3111696
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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LINKS
| Harry J. Smith, Table of n, a(n) for n=0,...,50
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EXAMPLE
| sigma(441) - usigma(441) = 241, a prime.
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PROG
| (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))))
(PARI) u(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d)) { n=-1; a=0; for (m=1, 10^9, if(isprime(b=sigma(m) - u(m)), if(b>a, a=b; write("b063760.txt", n++, " ", m); if (n==50, break))) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Aug 30 2009]
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CROSSREFS
| Cf. A048146.
Sequence in context: A063577 A087058 A046659 * A130448 A046451 A158142
Adjacent sequences: A063757 A063758 A063759 * A063761 A063762 A063763
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KEYWORD
| nonn
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AUTHOR
| Jason Earls (zevi_35711(AT)yahoo.com), Aug 24 2001
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EXTENSIONS
| Six more terms from Harry J. Smith (hjsmithh(AT)sbcglobal.net), Aug 30 2009
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