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 A120268 Numerator of Sum[1/(2k-1)^2,{k,1,n}]. 18
 1, 10, 259, 12916, 117469, 14312974, 2430898831, 487983368, 141433003757, 51174593563322, 51270597630767, 27164483940418988, 3400039831130408821, 30634921277843705014, 25789165074168004597399 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a((p-1)/2) is divisible by prime p>3. Denominators are A128492. The limit of the rationals r(n):=Sum[1/(2k-1)^2,{k,1,n}] for n->infinity is (Pi^2)/8 = (1-1/2^2)*Zeta(2) which is approximately 1.233700550. LINKS W. Lang, Rationals and limit. FORMULA a(n) = numerator[Sum[1/(2k-1)^2,{k,1,n}]]. a(n) = Denominator of (Pi^2)/2 - Zeta[2,(2n-1)/2] [From Artur Jasinski, Mar 03 2010] MATHEMATICA Numerator[Table[Sum[1/(2k-1)^2, {k, 1, n}], {n, 1, 25}]] CROSSREFS Cf. A025550, A007406. Sequence in context: A100743 A126468 A024293 * A001824 A024294 A183406 Adjacent sequences:  A120265 A120266 A120267 * A120269 A120270 A120271 KEYWORD frac,nonn AUTHOR Alexander Adamchuk, Jul 01 2006 STATUS approved

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