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A072301 Number of positive integers not exceeding n that are relatively prime to sigma(n). 0
1, 2, 2, 4, 2, 2, 4, 5, 9, 3, 4, 5, 6, 5, 5, 16, 6, 11, 8, 6, 11, 7, 8, 7, 25, 8, 11, 12, 8, 10, 16, 19, 11, 11, 12, 29, 18, 10, 17, 10, 12, 14, 20, 13, 14, 15, 16, 23, 31, 33, 17, 22, 18, 15, 19, 15, 23, 15, 16, 17, 30, 21, 30, 64, 19, 22, 32, 20, 23, 23, 24, 35, 36, 24, 37, 26, 26 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..77.

EXAMPLE

Among the positive integers not exceeding 12, the five numbers 1,3,5,9,11 are relatively prime to sigma(12)=28. Hence a(12)=5.

MATHEMATICA

r = {}; Do[ s = DivisorSigma[1, n]; j = 0; For[i = 1, i <= n, i++, If[GCD[s, i] == 1, j++ ]]; r = Append[r, j], {n, 1, 10^2}]; r

CROSSREFS

Sequence in context: A242734 A143230 A276604 * A127171 A215655 A118232

Adjacent sequences:  A072298 A072299 A072300 * A072302 A072303 A072304

KEYWORD

base,nonn

AUTHOR

Joseph L. Pe, Jul 14 2002

STATUS

approved

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Last modified April 23 14:15 EDT 2019. Contains 322386 sequences. (Running on oeis4.)