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A065556
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Numbers n such that sigma (phi ( n ) ) = sigma (sigma (n ) ) where phi is Euler's totient and sigma is the multiplicative sum-of-divisors function.
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1
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1, 367, 919, 1967, 3641, 4379, 5143, 7379, 11843, 12767, 13493, 15293, 21797, 26039, 28381, 29807, 30263, 30593, 30599, 30887, 37523, 40199, 48559, 49781, 51101, 51397, 55277, 62573, 67223, 72433, 73979, 87047, 89255, 89851, 95393
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,1000
Walter Nissen, Home Page (listed in lieu of email address)
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FORMULA
| sigma (phi ( n ) ) = sigma (sigma (n ) )
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EXAMPLE
| 367 is in the sequence because phi ( 367 ) = 366, sigma (367 ) = 368, sigma (366 ) = 744 = sigma (368 ).
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PROG
| (PARI) { n=0; for (m=1, 10^9, if (sigma(eulerphi(m)) == sigma(sigma(m)), write("b065556.txt", n++, " ", m); if (n==1000, return)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 22 2009]
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CROSSREFS
| A033632 A000010 A000203
Sequence in context: A054827 A059230 A060518 * A068357 A067891 A142579
Adjacent sequences: A065553 A065554 A065555 * A065557 A065558 A065559
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KEYWORD
| nonn
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AUTHOR
| Walter Nissen Nov 28 2001
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