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A121976
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Increasing sequence of odd primes such that abundancy(a(1)*...*a(n)) < 2, where abundancy(k) = A000203(k)/k. Generates "near perfect numbers".
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0
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OFFSET
| 1,1
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LINKS
| Charles R Greathouse IV, Home Page [Listed in lieu of email address]
Valeryi Kuryshev, NMBRTHRY Archives, 2006
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FORMULA
| a(n) = nextprime(1 / (2 / abundancy(a(1) * ... * a(n-1)) - 1)) for n >= 4
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EXAMPLE
| a(5)=389 because abundancy(3*5*7*11*383) = 2.000013... > 2 and abundancy(3*5*7*11*389) = 1.999933... < 2.
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PROG
| (PARI) print(3); print(5); print(7); n=105; for(i=4, 7, k=nextprime(1 / (2 / abundancy(n) - 1)); print(k); );
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CROSSREFS
| Cf. A000396, A000203.
Sequence in context: A068831 A109862 A069804 * A070334 A137700 A195821
Adjacent sequences: A121973 A121974 A121975 * A121977 A121978 A121979
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KEYWORD
| nonn
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AUTHOR
| Charles R. Greathouse IV, Sep 05 2006
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