A082506 - OEIS

A082506

a(n) = gcd(2^n, n - phi(n)); largest power of 2 dividing cototient(n) = A051953(n).

2, 1, 1, 2, 1, 4, 1, 4, 1, 2, 1, 8, 1, 8, 1, 8, 1, 4, 1, 4, 1, 4, 1, 16, 1, 2, 1, 16, 1, 2, 1, 16, 1, 2, 1, 8, 1, 4, 1, 8, 1, 2, 1, 8, 1, 8, 1, 32, 1, 2, 1, 4, 1, 4, 1, 32, 1, 2, 1, 4, 1, 32, 1, 32, 1, 2, 1, 4, 1, 2, 1, 16, 1, 2, 1, 8, 1, 2, 1, 16, 1, 2, 1, 4, 1, 4, 1, 16, 1, 2, 1, 16, 1, 16, 1, 64, 1, 8, 1

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OFFSET

1,1

COMMENTS

a(n)=1 if and only if n is odd or n = 2. - Robert Israel, May 31 2018

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

Different from A069177, analogous sequence with totient, instead of cototient.

MAPLE

f:= n -> padic:-ordp(n - numtheory:-phi(n), 2):

map(f, [$1..100]); # Robert Israel, May 31 2018