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 A074400 Sum of the even divisors of 2n. 32
 2, 6, 8, 14, 12, 24, 16, 30, 26, 36, 24, 56, 28, 48, 48, 62, 36, 78, 40, 84, 64, 72, 48, 120, 62, 84, 80, 112, 60, 144, 64, 126, 96, 108, 96, 182, 76, 120, 112, 180, 84, 192, 88, 168, 156, 144, 96, 248, 114, 186, 144, 196, 108, 240, 144, 240, 160, 180, 120, 336, 124, 192 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also alternating row sums of A236106. - Omar E. Pol, Jan 23 2014 Could also be called the twice sigma function, see first formula. - Omar E. Pol, Feb 05 2014 LINKS Antti Karttunen, Table of n, a(n) for n = 1..16384 FORMULA a(n) = 2*sigma(n) = 2*A000203(n). Dirichlet g.f.: 2*zeta(s-1)*zeta(s). - Ilya Gutkovskiy, Jul 06 2016 EXAMPLE The even divisors of 12 are 12, 6, 4, 2, which sum to 24, so a(6) = 24. MAPLE with(numtheory): seq(2*sigma(n), n=1..65); MATHEMATICA f[n_] := Plus @@ Select[ Divisors[ 2n], EvenQ]; Array[f, 62] (* Robert G. Wilson v, Apr 09 2011 *) PROG (PARI) a(n) = 2 * sigma(n); \\ Joerg Arndt, Apr 14 2013 (PARI) a(n) = sumdiv(2*n, d, !(d%2) * d); \\ Michel Marcus, Jan 23 2014 CROSSREFS k times sigma(n), k=1..6: A000203, this sequence, A272027, A239050, A274535, A274536. Cf. A146076, which includes the zeros for odd n. Sequence in context: A002511 A074383 A107505 * A264598 A165607 A109440 Adjacent sequences:  A074397 A074398 A074399 * A074401 A074402 A074403 KEYWORD easy,nonn AUTHOR Joseph L. Pe, Nov 25 2002 EXTENSIONS More terms from Emeric Deutsch, May 24 2004 STATUS approved

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Last modified August 24 13:48 EDT 2019. Contains 326279 sequences. (Running on oeis4.)