A179878 - OEIS

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A179878

Numbers h such that h and h-1 have same antiharmonic mean of the numbers k < h such that gcd(k, h) = 1 and simultaneously this mean is integer (see A179882).

2, 11, 23, 47, 59, 83, 107, 167, 179, 227, 263, 266, 347, 359, 383, 455, 467, 470, 479, 494, 503, 506, 518, 563, 587, 590, 719, 782, 839, 863, 887, 890, 902, 911, 935, 983, 986, 1019, 1166, 1178, 1187, 1235, 1283, 1295, 1307, 1319, 1334, 1358, 1367, 1394

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Corresponding values of numbers h-1 see A179877. Subsequence of A179876, A179871 and A179883.

LINKS

Table of n, a(n) for n=1..50.

MATHEMATICA

With[{s = Partition[Table[Mean[#^2]/Mean[#] &@ Select[Range[n - 1], GCD[#, n] == 1 &], {n, 1400}], 2, 1]}, 1 + Position[s, _?(And[IntegerQ@ First@ #, SameQ @@ #] &), 1, Heads -> False][[All, 1]]] (* Michael De Vlieger, Jul 30 2018 *)

CROSSREFS

Cf. A179871, A179872, A179873, A179874, A179875, A179876, A179877, A179879, A179880, A179882, A179883, A179884, A179885, A179886, A179887, A179890, A179891.

Sequence in context: A375788 A031385 A294551 * A126916 A090424 A056637

Adjacent sequences: A179875 A179876 A179877 * A179879 A179880 A179881

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Jul 30 2010, Jul 31 2010

STATUS

approved