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 A067786 Numbers n such that phi(n) = 2*pi(n) where pi(n) = A000720(n) and phi(n) = A000010(n). 0
 11, 13, 27, 39, 63, 122, 124, 136, 152, 176, 224, 322, 364, 410, 460, 1086, 1164, 3432, 3612, 12012 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Next term > 10^6. - Michel Marcus, Nov 22 2013 There are no more terms < 10^10. Conjectured to be complete. - Donovan Johnson, Nov 24 2013 LINKS EXAMPLE pi(11) = 5 and phi(11) = 10, so 11 is in the sequence. pi(12) = 5 but phi(12) = 4, so 12 is not in the sequence. pi(13) = 6 and phi(13) = 12, so 13 is in the sequence. MATHEMATICA Select[Range[500000], 2PrimePi[#] == EulerPhi[#] &] (* Harvey P. Dale, Nov 22 2013 *) PROG (PARI) isok(n) = eulerphi(n) == 2*primepi(n); \\ Michel Marcus, Nov 22 2013 CROSSREFS Sequence in context: A295340 A153055 A146915 * A132245 A140567 A232880 Adjacent sequences:  A067783 A067784 A067785 * A067787 A067788 A067789 KEYWORD nonn AUTHOR Benoit Cloitre, Feb 06 2002 EXTENSIONS Corrected and extended by Michel Marcus, Nov 22 2013 Confirmed by Harvey P. Dale, Nov 22 2013 STATUS approved

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Last modified January 18 21:06 EST 2021. Contains 340262 sequences. (Running on oeis4.)