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 A088838 Numerator of the quotient sigma(3n)/sigma(n). 4
 4, 4, 13, 4, 4, 13, 4, 4, 40, 4, 4, 13, 4, 4, 13, 4, 4, 40, 4, 4, 13, 4, 4, 13, 4, 4, 121, 4, 4, 13, 4, 4, 13, 4, 4, 40, 4, 4, 13, 4, 4, 13, 4, 4, 40, 4, 4, 13, 4, 4, 13, 4, 4, 121, 4, 4, 13, 4, 4, 13, 4, 4, 40, 4, 4, 13, 4, 4, 13, 4, 4, 40, 4, 4, 13, 4, 4, 13, 4, 4, 364, 4, 4, 13, 4, 4, 13, 4, 4, 40 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 FORMULA From Robert Israel, Nov 19 2017: (Start) a(n) = (3^(2+A007949(n))-1)/2. G.f.: Sum_{k>=0} (3^(k+2)-1)*(x^(3^k)+x^(2*3^k))/(2*(1-x^(3^(k+1)))). (End) MAPLE A088838 := proc(n)     numtheory[sigma](3*n)/numtheory[sigma](n) ;     numer(%) ; end proc: seq(A088838(n), n=1..100) ; # R. J. Mathar, Nov 19 2017 seq((3^(2+padic:-ordp(n, 3))-1)/2, n=1..100); # Robert Israel, Nov 19 2017 MATHEMATICA k=3; Table[Numerator[DivisorSigma[1, k*n]/DivisorSigma[1, n]], {n, 1, 128}] PROG (PARI) a(n) = numerator(sigma(3*n)/sigma(n)) \\ Felix FrÃ¶hlich, Nov 19 2017 CROSSREFS Cf. A007949, A038712, A088837, A088839, A088840, A080278 (denominator), A000203. Sequence in context: A228612 A038804 A183362 * A127403 A276423 A052993 Adjacent sequences:  A088835 A088836 A088837 * A088839 A088840 A088841 KEYWORD easy,nonn,frac,look AUTHOR Labos Elemer, Nov 04 2003 STATUS approved

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Last modified July 22 10:41 EDT 2019. Contains 325219 sequences. (Running on oeis4.)