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 A146076 Sum of even divisors of n. 26
 0, 2, 0, 6, 0, 8, 0, 14, 0, 12, 0, 24, 0, 16, 0, 30, 0, 26, 0, 36, 0, 24, 0, 56, 0, 28, 0, 48, 0, 48, 0, 62, 0, 36, 0, 78, 0, 40, 0, 84, 0, 64, 0, 72, 0, 48, 0, 120, 0, 62, 0, 84, 0, 80, 0, 112, 0, 60, 0, 144, 0, 64, 0, 126, 0, 96, 0, 108, 0, 96, 0, 182, 0, 76, 0, 120, 0, 112, 0, 180, 0, 84, 0, 192, 0, 88, 0, 168, 0, 156 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The usual OEIS policy is not to include sequences like this where alternate terms are zero; this is an exception. A074400 is the main entry. a(n) is also the total number of parts in all partitions of n into an even number of equal parts. - Omar E. Pol, Jun 04 2017 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..10000 FORMULA a(2k-1) = 0, a(2k) = 2*sigma(k) for positive k. Dirichlet g.f.: zeta(s - 1)*zeta(s)*2^(1 - s). - Geoffrey Critzer, Mar 29 2015 a(n) = A000203(n) - A000593(n). - Omar E. Pol, Apr 05 2016 L.g.f.: -log(Product_{ k>0 } (1-x^(2*k))) = Sum_{ n>=0 } (a(n)/n)*x^n. - Benedict W. J. Irwin, Jul 04 2016 a(n) = A000203(n)*(1 - (1/A038712(n))). - Omar E. Pol, Aug 01 2018 MAPLE A146076 := proc(n)     if type(n, 'even') then         2*numtheory[sigma](n/2) ;     else         0;     end if; end proc: # R. J. Mathar, Dec 07 2017 MATHEMATICA f[n_] := Plus @@ Select[Divisors[n], EvenQ]; Array[f, 150] (* Vincenzo Librandi, May 17 2013 *) a[n_] := DivisorSum[n, Boole[EvenQ[#]]*#&]; Array[a, 100] (* Jean-François Alcover, Dec 01 2015 *) Table[CoefficientList[Series[-Log[QPochhammer[x^2, x^2]], {x, 0, 60}], x][[n + 1]] n, {n, 1, 60}] (* Benedict W. J. Irwin, Jul 04 2016 *) PROG (PARI) vector(80, n, if (n%2, 0, sumdiv(n, d, d*(1-(d%2))))) \\ Michel Marcus, Mar 30 2015 (PARI) a(n) = if (n%2, 0, 2*sigma(n/2)); \\ Michel Marcus, Apr 01 2015 CROSSREFS Cf. A000203, A000593, A006128, A038712, A074400, A183063. Sequence in context: A290971 A178636 A046520 * A157195 A019781 A335959 Adjacent sequences:  A146073 A146074 A146075 * A146077 A146078 A146079 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Apr 09 2009 EXTENSIONS Corrected by Jaroslav Krizek, May 07 2011 STATUS approved

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Last modified November 29 01:03 EST 2020. Contains 338755 sequences. (Running on oeis4.)