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A176797 Antiharmonic means of divisors of antiharmonic numbers. 8
1, 3, 7, 11, 13, 21, 21, 43, 35, 43, 61, 63, 85, 111, 77, 157, 91, 129, 119, 147, 185, 171, 273, 183, 255, 343, 231, 301, 245, 255, 333, 313, 507, 301, 455, 481, 521, 425, 471, 547, 473, 455, 813, 441, 931, 629, 559 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Values of sigma_2(n) / sigma(n) corresponding to terms of A020487(n), where sigma_2(n) is the sum of squares of divisors of n (A001157) and sigma(n) is the sum of the divisors of n (A000203).

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = (A001157(A020487(n))) / (A000203(A020487(n))).

EXAMPLE

For n = 4; a(4) = 11 because A020487(4) = 16; A001157(16) = 341, A000203(n) = 31, antiharmonic means of divisors of 16 = 341 / 31 = 11.

MATHEMATICA

Select[DivisorSigma[2, #]/DivisorSigma[1, #] & /@ Range[1000], IntegerQ] (* Amiram Eldar, Sep 18 2019 *)

CROSSREFS

Sequence in context: A310198 A310199 A176800 * A078098 A154831 A206944

Adjacent sequences:  A176794 A176795 A176796 * A176798 A176799 A176800

KEYWORD

nonn,look

AUTHOR

Jaroslav Krizek, Apr 26 2010

STATUS

approved

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Last modified July 31 23:16 EDT 2021. Contains 346377 sequences. (Running on oeis4.)