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 A294521 Denominators of the partial sums of the reciprocals of the dodecagonal numbers (k + 1)*(5*k + 1) = A051624(k+1), for k >= 0. 3
 1, 12, 44, 704, 73920, 320320, 9929920, 89369280, 3664140480, 84275231040, 1432678927680, 1432678927680, 87393414588480, 87393414588480, 6204932435782080, 14736714534982440, 132630430814841960, 5703108525038204280, 5703108525038204280, 18249947280122253696, 1843244675292347623296 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The corresponding numerators are given in A294520. Details are found there. LINKS FORMULA a(n) = denominator(V(5,1;n)) with V(5,1;n) = Sum_{k=0..n} 1/((k + 1)*(5*k + 1)) = Sum_{k=0..n} 1/A051624(k+1) = (1/4)*Sum_{k=0..n} (1/(k + 1/5) - 1/(k+1)). For the formula in terms of the digamma function see A294520. EXAMPLE See A294520 for the rationals. PROG (PARI) a(n) = denominator(sum(k=0, n, 1/((k + 1)*(5*k + 1)))); \\ Michel Marcus, Nov 15 2017 CROSSREFS Cf. A294520. Sequence in context: A007899 A100156 A320998 * A309817 A340305 A194284 Adjacent sequences:  A294518 A294519 A294520 * A294522 A294523 A294524 KEYWORD nonn,frac,easy AUTHOR Wolfdieter Lang, Nov 15 2017 STATUS approved

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Last modified January 21 22:54 EST 2021. Contains 340359 sequences. (Running on oeis4.)