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return c[0] # Chai Wah Wu, Feb 05 2024
(Python)
from collections import Counter
from sympy import divisors
def A369873(n):
c = {0:1}
for d in divisors(n, generator=True):
b = Counter()
for j in c:
a = c[j]
b[j+d] += a
b[j-d] += a
c = b
return c[0] # Chai Wah Wu, Feb 05 2024
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From Joerg Arndt, Feb 04 2024: (Start)
a(n) != 0 (only) for n in A083207.
a(n) = 2 * A083206(n). (End)
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a(n) is the constant term in the expansion of Product_{d|n} (x^d + 1/x^d).
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