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A163666 Numbers n such that n=prime(sigma(phi(pi(n)))). 1
2, 5, 47, 107, 1613, 5653, 21557, 230047, 821603, 8145173, 47073007, 68939141, 76040521, 196388147, 240595631, 433046543, 1085166671, 2269551127, 4670405591, 9784786813, 104484802043, 420065905307, 474962067289, 2616252796471, 5804170333301 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

It is obvious that all terms are primes.

LINKS

Table of n, a(n) for n=1..25.

FORMULA

a(n) = A000040(A018784(n))

MATHEMATICA

Do[If[n=Prime[m]; m==DivisorSigma[1, EulerPhi[PrimePi[n]]], Print[n]], {m, 235000000}]

CROSSREFS

Cf. A000010, A000040, A000720, A000203, A163665.

Sequence in context: A023273 A041729 A078665 * A093552 A060808 A099658

Adjacent sequences:  A163663 A163664 A163665 * A163667 A163668 A163669

KEYWORD

nonn

AUTHOR

Farideh Firoozbakht, Aug 04 2009

EXTENSIONS

Formula and six more terms from Max Alekseyev, Jun 25 2011

STATUS

approved

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Last modified September 22 16:50 EDT 2020. Contains 337291 sequences. (Running on oeis4.)