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A039777
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phi(a(n)) is equal to the sum of (the product of prime factors and the products of exponents) of (a(n)-1).
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0
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2, 5, 21, 45, 285, 765, 27645, 196605, 41067645, 72787965, 250871805, 4295098365, 12884901885, 23307153405
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Next term if it exists is >= 10^8.
a(15) > 3*10^10. - Donovan Johnson
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EXAMPLE
| phi(21)=12, 20=2^2*5^1, (2*5)+(2*1)=12.
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CROSSREFS
| Cf. A000010, A039696.
Sequence in context: A003163 A088498 A190117 * A000941 A000131 A152801
Adjacent sequences: A039774 A039775 A039776 * A039778 A039779 A039780
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KEYWORD
| nonn,hard
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AUTHOR
| Olivier Gerard (olivier.gerard(AT)gmail.com)
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EXTENSIONS
| More terms from Jud McCranie (JudMcCranie(AT)ugaalum.uga.edu)
Corrected example and a(11)-a(14) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Nov 14 2010
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