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A280685
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a(n) = sum of the divisors of the product of the divisors of n.
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2
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1, 3, 4, 15, 6, 91, 8, 127, 40, 217, 12, 5080, 14, 399, 403, 2047, 18, 16395, 20, 19812, 741, 931, 24, 991111, 156, 1281, 1093, 50800, 30, 2929531, 32, 65535, 1729, 2149, 1767, 30203052, 38, 2667, 2379, 6397171, 42, 10506551, 44, 185928, 170508, 3871, 48
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OFFSET
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1,2
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LINKS
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FORMULA
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a(p) = p + 1 for p = primes (A000040).
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EXAMPLE
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For n = 4; a(n) = sigma (1*2*4) = sigma(8) = 15.
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PROG
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(Magma) [&+[d: d in Divisors(&*[d: d in Divisors(n)])]: n in [1..100]]
(Python)
from math import isqrt
from sympy import divisor_sigma
def A280685(n): return divisor_sigma((isqrt(n) if (c:=divisor_count(n)) & 1 else 1)*n**(c//2)) # Chai Wah Wu, Jun 25 2022
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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