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A009223 a(n) = gcd(sigma(n), phi(n)). 19
1, 1, 2, 1, 2, 2, 2, 1, 1, 2, 2, 4, 2, 6, 8, 1, 2, 3, 2, 2, 4, 2, 2, 4, 1, 6, 2, 4, 2, 8, 2, 1, 4, 2, 24, 1, 2, 6, 8, 2, 2, 12, 2, 4, 6, 2, 2, 4, 3, 1, 8, 2, 2, 6, 8, 24, 4, 2, 2, 8, 2, 6, 4, 1, 12, 4, 2, 2, 4, 24, 2, 3, 2, 6, 4, 4, 12, 24, 2, 2, 1, 2, 2, 8, 4, 6, 8, 20, 2, 6, 8, 4, 4, 2, 24, 4, 2, 3, 12, 1, 2, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) = gcd(A000203(n),A000010(n)).

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

MATHEMATICA

Table[GCD[DivisorSigma[1, n], EulerPhi[n]], {n, 110}] (* Harvey P. Dale, Aug 10 2011 *)

PROG

(PARI) a(n)=gcd(sigma(n=factor(n)), eulerphi(n)) \\ Charles R Greathouse IV, Nov 27 2013

(Haskell)

a009223 n = gcd (a000203 n) (a000010 n)

-- Reinhard Zumkeller, Jan 19 2014

CROSSREFS

Sequence in context: A082064 A082055 A073812 * A110244 A309020 A278495

Adjacent sequences:  A009220 A009221 A009222 * A009224 A009225 A009226

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified December 13 12:37 EST 2019. Contains 329968 sequences. (Running on oeis4.)