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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..22001

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. A186891, A283991, A294892, A294893, A294894.

Cf. also A294881, A294901.

Differs from A087624 for the first time at n=50.

Sequence in context: A333750 A072670 A087624 * A294879 A085122 A329867

Adjacent sequences:  A294888 A294889 A294890 * A294892 A294893 A294894

KEYWORD

nonn

AUTHOR

Antti Karttunen, Nov 10 2017

STATUS

approved

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Last modified September 17 14:07 EDT 2021. Contains 347478 sequences. (Running on oeis4.)