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 A260659 Denominators of a BBP-like formula for 4*Pi/sqrt(27). 2
 2, 80, 3584, 1760, 745472, 4456448, 99614720, 265289728, 10905190400, 54492397568, 1065151889408, 1277752770560, 96619584290816, 450799767388160, 8321103999008768, 19017153114013696, 689613692941107200, 3102980143258271744, 55484347409204510720, 30822635849723674624 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS 4*Pi/sqrt(27) = Sum_{n >= 0} (-1/8)^n*(2/(3*n+1)+1/(3*n+2)). LINKS Paolo Xausa, Table of n, a(n) for n = 0..1000 David H. Bailey, A Compendium of BBP-Type Formulas for Mathematical Constants. David Brink, Nilakantha's accelerated series for pi, Acta Arith. 171 (2015), 293-308. FORMULA a(n) = denominator((-1/8)^n*(2/(3*n+1)+1/(3*n+2))). MATHEMATICA A260659[n_] := Denominator[(-1/8)^n*(2/(3*n + 1) + 1/(3*n + 2))]; Array[A260659, 25, 0] (* Paolo Xausa, Jun 19 2024 *) PROG (PARI) a(n) = denominator((-1/8)^n*(2/(3*n+1)+1/(3*n+2))); \\ Michel Marcus, Nov 15 2015 (Magma) [Denominator((-1/8)^n*(2/(3*n+1)+1/(3*n+2))): n in [0..60]]; // Vincenzo Librandi, Nov 20 2015 CROSSREFS Cf. A073010, A260658 (numerators). Sequence in context: A073499 A222826 A123828 * A351854 A210277 A008563 Adjacent sequences: A260656 A260657 A260658 * A260660 A260661 A260662 KEYWORD nonn,frac AUTHOR David Brink, Nov 13 2015 EXTENSIONS More terms from Michel Marcus, Nov 15 2015 STATUS approved

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Last modified September 11 23:02 EDT 2024. Contains 375842 sequences. (Running on oeis4.)