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 A228970 Triangle of denominators of the coefficients t(n,k) in the formula B(2n) = -sum_{k=1..n-1} t(n,k)*B(2k)*B(2n-2k), where the B() are the even-indexed Bernoulli numbers. 2
 5, 7, 7, 85, 17, 85, 341, 341, 341, 341, 455, 91, 65, 91, 455, 5461, 5461, 5461, 5461, 5461, 5461, 4369, 4369, 21845, 257, 21845, 4369, 4369, 9709, 9709, 1387, 9709, 9709, 1387, 9709, 9709 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS GCD of rows (5, 7, 17, 341, 13, 5461 ...) are Zsigmondy numbers A064080. - Paul Curtz, Sep 13 2013 REFERENCES George Boros and Victor H. Moll, Irresistible Integrals: Symbolics, Analysis and Experiments in the Evaluation of Integrals, Cambridge University Press (2006), p. 100. LINKS Jean-François Alcover, Table of n, a(n) for n = 2..105 EXAMPLE 6/5; 5/7,        25/7; 28/85,     70/17,  588/85; 45/341, 1050/341, 4410/341, 3825/341; ... MATHEMATICA Table[(2^(2*k) - 1)/(2^(2*n) - 1)* Binomial[2*n, 2*k], {n, 2, 9}, {k, 1, n-1}] // Flatten // Denominator CROSSREFS Cf. A228969 (numerators), A064080 (Zsigmondy numbers). Sequence in context: A126992 A028316 A019163 * A266712 A021177 A091662 Adjacent sequences:  A228967 A228968 A228969 * A228971 A228972 A228973 KEYWORD frac,nonn,tabl AUTHOR Jean-François Alcover, Sep 10 2013 STATUS approved

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Last modified December 11 23:44 EST 2019. Contains 329945 sequences. (Running on oeis4.)