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Search: id:A064519
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| A064519 |
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Numbers n such that usigma(n) / tau(n) is prime. |
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+0
1
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| 3, 5, 6, 13, 18, 20, 27, 37, 50, 61, 73, 96, 157, 193, 242, 277, 313, 397, 421, 457, 486, 541, 613, 661, 673, 722, 733, 757, 877, 997, 1093, 1153, 1201, 1213, 1237, 1321, 1381, 1453, 1621, 1657, 1682, 1753, 1873, 1933, 1993, 2017, 2137, 2341, 2473, 2557
(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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PROGRAM
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(PARI) {usigma(n, s=1, fac, i)= fac=factor(n); for(i=1, matsize(fac)[1], s=s*(1+fac[i, 1]^fac[i, 2]) ); return(s); } for(n=1, 5000, if(usigma(n)%numdiv(n)==0 && isprime(usigma(n)/numdiv(n)), print1(n, " ")))
(PARI) usigma(n)= { local(f, s=1); f=factor(n); for(i=1, matsize(f)[1], s*=1 + f[i, 1]^f[i, 2]); return(s) } { n=0; for (m=1, 10^9, if ((u=usigma(m))%(d=numdiv(m))==0 && isprime(u/d), write("b064519.txt", n++, " ", m); if (n==1000, break)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Sep 17 2009]
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CROSSREFS
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Cf. A034448, A000005.
Sequence in context: A088082 A139013 A108337 this_sequence A048968 A092862 A112863
Adjacent sequences: A064516 A064517 A064518 this_sequence A064520 A064521 A064522
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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), Oct 07 2001
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