%I #13 Oct 19 2017 10:38:28

%S 2,1,1,1,5,1,84,11,184,15,193248,23,19056960,833,33740,64035,

%T 520105017600,2473,130859579289600,203685,963513600,23748417,

%U 16397141420298240000,645119,555804546402631680,8527366575

%N a(n) = 2*(A056855(n)) /(phi(n)*n), where phi() is the Euler phi function.

%C Conjecture: this sequence consists completely of integers.

%C From Leudesdorf's theorem this is an integer sequence. - _Benoit Cloitre_, Nov 13 2004

%D G. H. Hardy and E. M. Wright, Introduction to the theory of numbers, fifth edition, Oxford Science Publication, pp. 100-102

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/LeudesdorfTheorem.html">Leudesdorf Theorem</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/BauersIdenticalCongruence.html">Bauers Identical Congruence</a>

%e a(6) = 2*(1 + 1/5)*1*5/(6*2) = 1.

%t f[n_] := Block[{k = Select[Range[n], GCD[ #, n] == 1 &]}, 2Plus @@ (Times @@ k*Plus @@ 1/k)/EulerPhi[n]/n]; Table[ f[n], {n, 26}] (* _Robert G. Wilson v_, Nov 16 2004 *)

%Y Cf. A056855, A000010.

%Y Cf. A093600.

%K nonn

%O 1,1

%A _Leroy Quet_, Nov 12 2004

%E More terms from _Don Reble_, Nov 12 2004, who remarks that the conjecture is true for n <= 5000.