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URL: https://oeis.org/A260659

⇱ A260659 - OEIS

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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
OFFSET
0,1
COMMENTS
4*Pi/sqrt(27) = Sum_{n >= 0} (-1/8)^n*(2/(3*n+1)+1/(3*n+2)).
LINKS
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: A378312 A222826 A123828 * A351854 A210277 A008563
KEYWORD
nonn,frac
AUTHOR
David Brink, Nov 13 2015
EXTENSIONS
More terms from Michel Marcus, Nov 15 2015
STATUS
approved