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A073757 Number of numbers "related" to n: either divisors or terms in RRS of n. 23
1, 2, 3, 4, 5, 5, 7, 7, 8, 7, 11, 9, 13, 9, 11, 12, 17, 11, 19, 13, 15, 13, 23, 15, 22, 15, 21, 17, 29, 15, 31, 21, 23, 19, 27, 20, 37, 21, 27, 23, 41, 19, 43, 25, 29, 25, 47, 25, 44, 25, 35, 29, 53, 25, 43, 31, 39, 31, 59, 27, 61, 33, 41, 38, 51, 27, 67, 37, 47, 31, 71, 35, 73 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

RRS of n means reduced residue system modulo n. One considers here the smallest positive one. - Wolfdieter Lang, Jan 16 2016

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = n - A045763(n) = d(n) + phi(n) - 1 = A000005(n) + A000010(n) - 1.

If p is prime then a(p) = p.

Row sums of triangle A134673. - Gary W. Adamson, Nov 05 2007

MATHEMATICA

DivisorSigma[0, #] + EulerPhi[#] - 1 & /@ Range[73] (* Jayanta Basu, Jul 09 2013 *)

PROG

(PARI) a(n)=my(f=factor(n)); numdiv(f)+eulerphi(f)-1 \\ Charles R Greathouse IV, Nov 14 2014

CROSSREFS

Cf. A000004, A000010, A045763, A134673.

Sequence in context: A094802 A075084 A086593 * A088468 A049448 A130044

Adjacent sequences:  A073754 A073755 A073756 * A073758 A073759 A073760

KEYWORD

nonn

AUTHOR

Labos Elemer, Aug 08 2002

STATUS

approved

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Last modified August 9 20:09 EDT 2020. Contains 336326 sequences. (Running on oeis4.)