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 A039782 phi(n) is equal to the sum of the prime-power components of n-1. 0
 3, 5, 16, 17, 22, 36, 40, 257, 65537 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Close to Fermat primes (A019434). Next term if it exists is greater than 10^8. - Jud McCranie, Dec 09 1999 Next term > 10^9. - Michel Marcus, Jun 03 2014 a(10) > 10^13, if it exists. - Giovanni Resta, Dec 03 2018 LINKS Table of n, a(n) for n=1..9. EXAMPLE phi(36)=12, 35=5^1*7^1, (5^1)+(7^1)=12. MATHEMATICA Select[Range[3, 66000], EulerPhi[#]==Total[#[[1]]^#[[2]]&/@FactorInteger[ #-1]]&] (* Harvey P. Dale, Nov 30 2018 *) PROG (PARI) isok(n) = (f = factor(n-1)) && (sum(i=1, #f~, f[i, 1]^f[i, 2]) == eulerphi(n)); \\ Michel Marcus, Jun 03 2014 CROSSREFS Cf. A000010, A008475. Sequence in context: A325257 A006593 A115724 * A331638 A080056 A330055 Adjacent sequences: A039779 A039780 A039781 * A039783 A039784 A039785 KEYWORD nonn,more AUTHOR Olivier Gérard, Dec 11 1999 STATUS approved

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Last modified September 18 03:51 EDT 2024. Contains 375995 sequences. (Running on oeis4.)