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A230292 a(n) = Sum_{i=1..n} d(24*i+9) - Sum_{i=1..n} d(6*i+3), where d(n) = A000005(n). 3

%I

%S 1,1,2,6,6,8,6,6,11,9,13,15,14,18,20,18,14,19,21,21,25,21,25,31,33,33,

%T 31,29,33,36,32,32,34,40,40,42,41,37,49,51,51,49,47,51,52,54,50,54,54,

%U 58,60,52,56,64,62,66,68,64,68,74,72,68,73,75,75,75,77,77,85,83,79,77,72,84,88,88,84,92,94,90,98,90

%N a(n) = Sum_{i=1..n} d(24*i+9) - Sum_{i=1..n} d(6*i+3), where d(n) = A000005(n).

%H Jorge Luis Cimadevilla Villacorta, <a href="http://www.jstor.org/stable/10.4169/amer.math.monthly.120.09.832">Certain inequalities associated with the divisor function</a>, Amer. Math. Monthly, 120 (2013), 832-837. (Shows that a(n) >= 0.)

%p See A230290.

%o (PARI) vector(100, n, sum(i=1, n, numdiv(24*i+9)) - sum(i=1, n, numdiv(6*i+3))) \\ _Michel Marcus_, Oct 09 2014

%Y Cf. A000005, A230290-A230296.

%K nonn

%O 1,3

%A _N. J. A. Sloane_, Oct 17 2013

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Last modified July 12 18:03 EDT 2020. Contains 335666 sequences. (Running on oeis4.)