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%I #10 Nov 17 2017 04:06:47
%S 2,7,252,2142,58905,1060290,16964640,627691680,627691680,29501508960,
%T 383519616480,7286872713120,225893054106720,15134834625150240,
%U 15134834625150240,15134834625150240,620528219631159840,17995318369303635360,413892322493983613280,8029511056383282097632
%N Denominators of the partial sums of the reciprocals of twice the heptagonal numbers (k + 1)*(5*k + 2) = A135706(k+1) = 2*A000566(k+1), for k >= 0.
%C The corresponding numerators are given in A294826. Details are found there.
%F a(n) = denominator(V(5,2;n)) with V(5,2;n) = Sum_{k=0..n} 1/((k + 1)*(5*k + 2)) = Sum_{k=0..n} 1/A135706(k+1) = (1/3)*Sum_{k=0..n} (1/(k + 2/5) - 1/(k+1)). For this formula in terms of the digamma function see A294826.
%e See A294826 for the rationals.
%o (PARI) a(n) = denominator(sum(k=0, n, 1/((k + 1)*(5*k + 2)))); \\ _Michel Marcus_, Nov 17 2017
%Y Cf. A000566, A135706, A294826.
%K nonn,frac,easy
%O 0,1
%A _Wolfdieter Lang_, Nov 16 2017
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