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A051536
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a(n) = least common multiple of {1, 4, 7, 10, 13 ..., 3n+1} (A016777).
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8
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1, 4, 28, 140, 1820, 7280, 138320, 1521520, 7607600, 7607600, 235835600, 4009205200, 148340592400, 148340592400, 6378645473200, 146708845883600, 1026961921185200, 1026961921185200, 1026961921185200, 29781895714370800
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OFFSET
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0,2
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COMMENTS
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This sequence coincides with the sequence of denominators of 1 + 1/4 + 1/7 + 1/10 + ... + 1/(3*n + 1) for n < 29. - T. D. Noe, Aug 04 2004
The sequence coincides with the sequence of denominators of 1 - 1/4 + 1/7 - 1/10 + ... + (-1)^n/(3*n + 1) for n < 45. - Peter Bala, Feb 19 2024
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LINKS
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EXAMPLE
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a(4) = lcm of {1, 4, 7, 10, 13} = 1820.
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MATHEMATICA
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Table[ Denominator[ Sum[1/i, {i, 1/3, n}]], {n, 1, 20}]
Table[ Apply[ LCM, Join[{1}, Table[1 + 3i, {i, 0, n}]]], {n, 0, 19}]
Table[Denominator[Total[1/Range[1, 3n+1, 3]]], {n, 0, 29}]
Module[{nn=30, lst}, lst=3*Range[0, nn]+1; Table[LCM@@Take[lst, n], {n, nn}]] (* Harvey P. Dale, Sep 30 2012 *)
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PROG
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(Magma) k:=58; [Lcm([h: h in [1..j by 3]]): j in [1..k by 3]]; // Bruno Berselli, May 03 2011
(Haskell)
a051536 n = a051536_list !! (n-1)
a051536_list = scanl1 lcm a016777_list
-- Reinhard Zumkeller, Feb 28 2013, Feb 10 2012
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CROSSREFS
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KEYWORD
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easy,frac,nice,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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