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A091818 Sum of the even proper divisors of 2n. Sum of the even divisors of 2n that are less than 2n. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n) = A074400(2n) - 2n. - Michel Marcus, Jan 14 2014
a(n) = Sum_{d|2n, d<2n, d even} d. - Wesley Ivan Hurt, Mar 02 2022
a(n) = 2 * A001065(n). - Alois P. Heinz, Mar 02 2022
EXAMPLE
The sum of the even divisors of 18 that are less than 18 is 8 = 2+6.
MATHEMATICA
Table[Total[Select[Most[Divisors[2 n]], EvenQ]], {n, 70}] (* Harvey P. Dale, Apr 28 2023 *)
PROG
(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
print([a(n) for n in range(1, 101)]) # Indranil Ghosh, Oct 30 2017
CROSSREFS
Sequence in context: A283362 A337524 A324047 * A324202 A278240 A263077
KEYWORD
easy,nonn
AUTHOR
Mohammad K. Azarian, Mar 07 2004
EXTENSIONS
More terms from Michel Marcus, Jan 14 2014
STATUS
approved

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Last modified March 19 04:58 EDT 2024. Contains 370952 sequences. (Running on oeis4.)