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A036098
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Centered cube numbers: a(n) = (n+1)^20 + n^20.
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3
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1, 1048577, 3487832977, 1102998412177, 96466943268401, 3751525871703601, 83448424737674977, 1232713770904458977, 13310586963663775777, 112157665459056928801, 772749994932560009201, 4506509987380035131377
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OFFSET
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0,2
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COMMENTS
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Never prime because a(n) = (2n^4 + 4n^3 + 6n^2 + 4n + 1) * (n^16 + 8n^15 + 76n^14 + 392n^13 + 1394n^12 + 3632n^11 + 7112n^10 + 10656n^9 + 12376n^8 + 11220n^7 + 7942n^6 + 4356n^5 + 1819n^4 + 560n^3 + 120n^2 + 16n + 1). Semiprime for n in {1, 13, 14, 54, 162, ...}. - Jonathan Vos Post, Aug 27 2011
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LINKS
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EXAMPLE
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a(1) = 1^20 + (1+1)^20 = 1048577 = 17 * 61681, which is semiprime.
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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