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A084921
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a(n) = lcm(p-1, p+1) where p is the n-th prime.
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17
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3, 4, 12, 24, 60, 84, 144, 180, 264, 420, 480, 684, 840, 924, 1104, 1404, 1740, 1860, 2244, 2520, 2664, 3120, 3444, 3960, 4704, 5100, 5304, 5724, 5940, 6384, 8064, 8580, 9384, 9660, 11100, 11400, 12324, 13284, 13944, 14964, 16020, 16380
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OFFSET
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1,1
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COMMENTS
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This sequence consists of terms of sequences A055523 and A055527 for prime n > 2. - Toni Lassila (tlassila(AT)cc.hut.fi), Feb 02 2004
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LINKS
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FORMULA
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Product_{n>=1} (1 + 1/a(n)) = 2. - Amiram Eldar, Jan 23 2021
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MATHEMATICA
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PROG
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(Haskell)
a084921 n = lcm (p - 1) (p + 1) where p = a000040 n
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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