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Search: id:A128507
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| A128507 |
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Denominators of partial sums for a series for 3*sqrt(2)*(Pi^3)/2^7. |
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+0
4
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| 1, 27, 3375, 1157625, 31255875, 41601569625, 91398648466125, 91398648466125, 449041559914072125, 3079976059450620705375, 439996579921517243625, 5353438387905100303185375, 669179798488137537898171875
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OFFSET
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0,2
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COMMENT
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The numerators are given in A128506.
See the comments and the W. Lang link under A128506.
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FORMULA
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a(n)=denominator(r(n)) with the rationals r(n):=sum(S(2*k,sqrt(2))/(2*k+1)^3,k=0..n) with Chebyshev's S-Polynomials S(2*k,sqrt(2))=[1,1,-1,-1] periodic sequence with period 4. See A057077.
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EXAMPLE
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Rationals r(n): [1, 28/27, 3473/3375, 1187864/1157625, 32115203/31255875,...].
3*sqrt(2)*(Pi^3)/2^7 = +1/1^3 +1/3^3 -1/5^3 -1/7^3 +1/9^3 +1/11^3 -1/13^3 -1/15^3 ++--
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CROSSREFS
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Sequence in context: A132645 A017559 A069076 this_sequence A166750 A046367 A059795
Adjacent sequences: A128504 A128505 A128506 this_sequence A128508 A128509 A128510
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KEYWORD
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nonn,frac,easy
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AUTHOR
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Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de) Apr 04 2007
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