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 A039778 phi(n) is equal to the sum of prime factors and exponents of n+1. 0
 32, 38, 54, 56, 84, 20720 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(7) > 10^8. - Naohiro Nomoto, Jun 21 20a a(7) > 10^9. - Michel Marcus, Jun 03 2014 a(7) > 10^12. - Giovanni Resta, Jun 11 2016 LINKS EXAMPLE phi(38)=18, 39=3^1*13^1, 3+1+13+1=18. MATHEMATICA Select[Range[30000], EulerPhi[#] == Plus @@ Flatten@ FactorInteger[# + 1] &] (* Giovanni Resta, Jun 11 2016 *) PROG (PARI) isok(n) = (f = factor(n+1)) && (sum(i=1, #f~, f[i, 2]) + sum(i=1, #f~, f[i, 1]) == eulerphi(n)); \\ Michel Marcus, Jun 03 2014 CROSSREFS Cf. A000010, A008474. Sequence in context: A082591 A070624 A178099 * A217060 A240246 A167309 Adjacent sequences:  A039775 A039776 A039777 * A039779 A039780 A039781 KEYWORD nonn,more AUTHOR STATUS approved

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Last modified January 20 02:51 EST 2019. Contains 319323 sequences. (Running on oeis4.)