1,1

It seems that for each n, a(n) exists and the set An={m|n*pi(m)=phi(m)} is finite, for example A1={2,3,4,8,10,14,20,90}(elements of A1 are terms of the sequenc A037171), A2={11,13,27,39,63,122,124, 136,152,176,224,322,364,410,460,1086,1164,3432,3612},... . According to the definition, a(n) is the smallest element of An. For n<19, 3 doesn't divide a(n), is this true for all terms of the sequence?

a[n_]:=(For[m=1, n*PrimePi[m]!=EulerPhi[m], m++ ];m)

a(18)=189963073 because 18*pi(189963073)=phi(189963073) and for m<189963073 18*pi(m)!= phi(m).

a[n_]:=(For[m=1, n*PrimePi[m]!=EulerPhi[m], m++ ]; m); Do[Print[a[n]], {n, 18}]

Cf. A037171.

Sequence in context: A140553 A038607 A079009 this_sequence A059673 A166989 A143550

Adjacent sequences: A097648 A097649 A097650 this_sequence A097652 A097653 A097654

more,nonn

Farideh Firoozbakht (mymontain(AT)yahoo.com), Sep 07 2004