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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.

%I A091818 #34 Apr 28 2023 16:25:19
%S A091818 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,
%T A091818 56,2,84,2,62,30,40,26,110,2,44,34,100,2,108,2,80,66,52,2,152,16,86,
%U A091818 42,92,2,132,34,128,46,64,2,216,2,68,82,126,38,156,2,116
%N A091818 Sum of the even proper divisors of 2n. Sum of the even divisors of 2n that are less than 2n.
%H A091818 Antti Karttunen, <a href="/A091818/b091818.txt">Table of n, a(n) for n = 1..16384</a>
%F A091818 a(n) = A074400(2n) - 2n. - _Michel Marcus_, Jan 14 2014
%F A091818 a(n) = Sum_{d|2n, d<2n, d even} d. - _Wesley Ivan Hurt_, Mar 02 2022
%F A091818 a(n) = 2 * A001065(n). - _Alois P. Heinz_, Mar 02 2022
%e A091818 The sum of the even divisors of 18 that are less than 18 is 8 = 2+6.
%t A091818 Table[Total[Select[Most[Divisors[2 n]],EvenQ]],{n,70}] (* _Harvey P. Dale_, Apr 28 2023 *)
%o A091818 (PARI) a(n) = sumdiv(2*n, d, !(d%2) * d * (d<2*n)); \\ _Michel Marcus_, Jan 14 2014
%o A091818 (Python)
%o A091818 from sympy import divisors
%o A091818 def a(n): return sum(d for d in divisors(2*n) if d%2==0) - 2*n
%o A091818 print([a(n) for n in range(1, 101)]) # _Indranil Ghosh_, Oct 30 2017
%Y A091818 Cf. A001065, A032741, A091570, A074400, A173455.
%K A091818 easy,nonn
%O A091818 1,2
%A A091818 _Mohammad K. Azarian_, Mar 07 2004
%E A091818 More terms from _Michel Marcus_, Jan 14 2014