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A294891
Number of proper divisors d of n such that Stern polynomial B(d,x) is irreducible.
6
0, 0, 0, 1, 0, 2, 0, 1, 1, 2, 0, 2, 0, 2, 2, 1, 0, 2, 0, 2, 2, 2, 0, 2, 1, 2, 1, 2, 0, 3, 0, 1, 2, 2, 2, 2, 0, 2, 2, 2, 0, 3, 0, 2, 2, 2, 0, 2, 1, 3, 2, 2, 0, 2, 2, 2, 2, 2, 0, 3, 0, 2, 2, 1, 2, 3, 0, 2, 2, 3, 0, 2, 0, 2, 3, 2, 2, 3, 0, 2, 1, 2, 0, 3, 2, 2, 2, 2, 0, 3, 2, 2, 2, 2, 2, 2, 0, 2, 2, 3, 0, 3, 0, 2, 3
OFFSET
1,6
LINKS
FORMULA
a(n) = Sum_{d|n, d<n} A283991(d).
a(n) + A294892(n) = A032741(n).
a(n) = A294893(n) - A283991(n).
EXAMPLE
For n=50, with proper divisors [1, 2, 5, 10, 25], 2, 5, and 25 are larger than one and included in A186891, thus a(50) = 3.
PROG
(PARI)
ps(n) = if(n<2, n, if(n%2, ps(n\2)+ps(n\2+1), 'x*ps(n\2)));
A283991(n) = polisirreducible(ps(n));
A294891(n) = sumdiv(n, d, (d<n)*A283991(d));
CROSSREFS
Cf. also A294881, A294901.
Differs from A087624 for the first time at n=50.
Sequence in context: A333750 A072670 A087624 * A294879 A085122 A329867
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 10 2017
STATUS
approved