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A130420 a(n) = n-th positive integer which is coprime to n!!, where n!! = n*(n-2)*(n-4)..*(2 or 1). 1

%I

%S 1,3,4,7,8,17,16,23,19,37,29,43,37,59,41,67,53,73,62,83,67,101,79,107,

%T 83,127,89,137,103,149,113,157,122,173,128,181,139,197,146,211,158,

%U 227,173,233,179,251,194,263,199,271,206,281,223,293,227,311,233,331,251

%N a(n) = n-th positive integer which is coprime to n!!, where n!! = n*(n-2)*(n-4)..*(2 or 1).

%e 3!! = 3; the first number coprime to 3 is 1, the second one is 2, the third one is 4. Thus a(3) = 4.

%t a[n_] := Module[{in}, in = 0; k = 0; While[in != n, k++; If[GCD[n!!, k] == 1, in++ ]]; k]; Table[a[i], {i, 1, 80}] (* _Stefan Steinerberger_, May 30 2007 *)

%Y Cf. A130419, A119992.

%K less,nonn

%O 1,2

%A _Leroy Quet_, May 25 2007

%E More terms from _Stefan Steinerberger_, May 30 2007

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Last modified October 21 23:34 EDT 2021. Contains 348160 sequences. (Running on oeis4.)