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A091818
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Sum of the even proper divisors of 2n. Sum of the even divisors of 2n that are less than 2n.
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3
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0, 2, 2, 6, 2, 12, 2, 14, 8, 16, 2, 32, 2, 20, 18, 30, 2, 42, 2, 44, 22, 28, 2, 72, 12, 32, 26, 56, 2, 84, 2, 62, 30, 40, 26, 110, 2, 44, 34, 100, 2, 108, 2, 80, 66, 52, 2, 152, 16, 86, 42, 92, 2, 132, 34, 128, 46, 64, 2, 216, 2, 68, 82, 126, 38, 156, 2, 116
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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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EXAMPLE
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The sum of the even divisors of 18 that are less than 18 is 8 = 2+6.
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MATHEMATICA
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Table[Total[Select[Most[Divisors[2 n]], EvenQ]], {n, 70}] (* Harvey P. Dale, Apr 28 2023 *)
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PROG
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(PARI) a(n) = sumdiv(2*n, d, !(d%2) * d * (d<2*n)); \\ Michel Marcus, Jan 14 2014
(Python)
from sympy import divisors
def a(n): return sum(d for d in divisors(2*n) if d%2==0) - 2*n
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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