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A295308
Characteristic function for A066694: a(n) = 1 if n < phi(sigma(n)), 0 otherwise.
2
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, 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, 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
OFFSET
1
FORMULA
a(n) = 1 if n < A062401(n), 0 otherwise.
MATHEMATICA
Array[Boole[# < EulerPhi@ DivisorSigma[1, #]] &, 120] (* Michael De Vlieger, Nov 22 2017 *)
PROG
(PARI) a(n) = n < eulerphi(sigma(n)); \\ Michel Marcus, Nov 23 2017
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 22 2017
STATUS
approved