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.

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

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

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

Cf. A000010, A008966, A007814, A053574, A353499.

Sequence in context: A353354 A284912 A192082 * A296066 A073070 A370702

Adjacent sequences: A353495 A353496 A353497 * A353499 A353500 A353501

Keyword

nonn

Author

Antti Karttunen, Apr 22 2022

Status

approved