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A294884
Number of divisors of n that are not irreducible when their binary expansion is interpreted as polynomial over GF(2).
5
1, 1, 1, 2, 2, 2, 1, 3, 2, 3, 1, 4, 1, 2, 3, 4, 2, 4, 1, 5, 2, 2, 2, 6, 2, 2, 3, 4, 2, 6, 1, 5, 2, 3, 3, 7, 1, 2, 2, 7, 1, 5, 2, 4, 5, 3, 1, 8, 2, 4, 3, 4, 2, 6, 2, 6, 2, 3, 1, 10, 1, 2, 4, 6, 3, 5, 1, 5, 3, 6, 2, 10, 1, 2, 4, 4, 2, 5, 2, 9, 4, 2, 2, 9, 4, 3, 2, 6, 2, 10, 1, 5, 2, 2, 3, 10, 1, 4, 4, 7, 2, 6, 1, 6, 6
OFFSET
1,4
COMMENTS
One more than the number of terms of A091242 that divide n: +1 is for divisor 1, which is also included in the count.
FORMULA
a(n) = Sum_{d|n} (1-A091225(d)).
a(n) + A294883(n) = A000005(n).
For n > 1, a(n) = 1 + A294882(n) - A091225(n).
PROG
(PARI) A294884(n) = sumdiv(n, d, !polisirreducible(Mod(1, 2)*Pol(binary(d))));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 09 2017
STATUS
approved