A176797 Antiharmonic means of divisors of antiharmonic numbers.

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

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