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A179871 Numbers h such that antiharmonic mean B(h) of the numbers k < h such that gcd(k, h) = 1 is integer. 23
1, 2, 5, 10, 11, 17, 22, 23, 29, 34, 41, 46, 47, 53, 55, 58, 59, 71, 82, 83, 85, 89, 91, 94, 101, 106, 107, 110, 113, 115, 118, 131, 133, 137, 142, 145, 149, 166, 167, 170, 173, 178, 179, 182, 187, 191, 197, 202, 205, 214 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers h such that B(h) = A053818(h) / A023896(h) = A175505(h) / A175506(h) is integer. Numbers h such that A175506(h) = 1. Complement of A179872. See A179873 (odd positive integers) for corresponding values A175505(a(n)). a(n) = union A003627 (primes of form 3n-1) and A179887.

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..2500

EXAMPLE

Example: a(9) = 29 because B(29) = A053818(29) / A023896(29) = 7714/406 = 19 (integer).

MATHEMATICA

B[n_] := Plus @@ ((ks = Select[Range[n], GCD[n, #] == 1 &])^2)/Plus @@ ks; Select[Range[215], IntegerQ[B[#]] &] (* Ivan Neretin, May 22 2015 *)

CROSSREFS

Cf. A179872, A179873, A179874, A179875, A179876, A179877, A179878, A179879, A179880, A179882, A179883, A179884, A179885, A179886, A179887, A179890, A179891.

Sequence in context: A163624 A257031 A167799 * A258116 A324812 A032874

Adjacent sequences:  A179868 A179869 A179870 * A179872 A179873 A179874

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Jul 30 2010, Jul 31 2010

STATUS

approved

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Last modified November 15 08:37 EST 2019. Contains 329144 sequences. (Running on oeis4.)