A163126 - OEIS

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A163126

a(1)=1. a(n) = the number of integers k, 1 <= k <= n-1, where a(k) is coprime to n-k.

1, 1, 2, 3, 3, 5, 4, 6, 6, 7, 4, 9, 7, 11, 9, 12, 9, 12, 12, 13, 11, 16, 14, 15, 15, 18, 15, 19, 17, 17, 19, 22, 20, 22, 22, 21, 24, 26, 23, 27, 25, 27, 26, 31, 24, 27, 27, 29, 31, 35, 29, 35, 36, 36, 35, 39, 34, 39, 35, 39, 39, 42, 39, 40, 39, 38, 43, 47, 37, 47, 44, 46, 47, 50, 46, 47, 49, 50, 52, 48, 51, 52, 54, 52, 53, 56, 52, 58, 55, 53, 60, 59, 60, 59, 60, 60, 61, 60, 60, 62

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

OFFSET

1,3

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

MATHEMATICA

t={1}; Do[AppendTo[t, Length[Select[Range[n-1], CoprimeQ[t[[#]], n-#] &]]], {n, 2, 100}]; t

CROSSREFS

A163127

Sequence in context: A159070 A373812 A088241 * A304818 A088922 A357658

Adjacent sequences: A163123 A163124 A163125 * A163127 A163128 A163129

KEYWORD

nonn

AUTHOR

Leroy Quet, Jul 21 2009

EXTENSIONS

More terms from Sean A. Irvine, Nov 29 2010

STATUS

approved