A295308 - OEIS

%I #12 Nov 23 2017 05:14:46

%S 0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,

%T 0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,

%U 0,0,0,1,0,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0

%N Characteristic function for A066694: a(n) = 1 if n < phi(sigma(n)), 0 otherwise.

%H Antti Karttunen, <a href="/A295308/b295308.txt">Table of n, a(n) for n = 1..65537</a>

%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>

%F a(n) = 1 if n < A062401(n), 0 otherwise.

%t Array[Boole[# < EulerPhi@ DivisorSigma[1, #]] &, 120] (* _Michael De Vlieger_, Nov 22 2017 *)

%o (PARI) a(n) = n < eulerphi(sigma(n)); \\ _Michel Marcus_, Nov 23 2017

%Y Cf. A000010, A000203, A062401, A066694, A295301, A295303, A295309.

%K nonn

%O 1

%A _Antti Karttunen_, Nov 22 2017