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A353498
a(n) = 1 if n > 1 and the 2-adic valuation of phi(n) does not exceed the 2-adic valuation of n-1, otherwise 0.
2
0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1
OFFSET
1
FORMULA
a(1) = 0, and for n > 1, a(n) = [A053574(n) <= A007814(n-1)], where [ ] is the Iverson bracket.
EXAMPLE
For n = 121, phi(121) = 110 = 2*5*11, while 120 = 2^3 * 3 * 5, thus as the exponent of 2 in 110 is <= the exponent in 120, a(121) = 1.
PROG
(PARI) A353498(n) = ((n>1)&&(valuation(eulerphi(n), 2)<=valuation(n-1, 2)));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 22 2022
STATUS
approved