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0, 4, 6, 28, 10, 94, 14, 140, 78, 194, 22, 574, 26, 326, 316, 620, 34, 1066, 38, 1218, 524, 686, 46, 2750, 310, 914, 780, 2086, 58, 3884, 62, 2604, 1084, 1466, 1004, 6370, 74, 1790, 1436, 5890, 82, 6716, 86, 4494, 3718, 2534, 94, 11966, 798, 5394, 2284
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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LINKS
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FORMULA
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For p prime, a(p) = 2p.
Sum_{k=1..n} a(k) ~ c * n^3, where c = zeta(3)/2 = 0.601028451579... . (End)
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MATHEMATICA
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a[n_] := DivisorSigma[1, n]^2 - DivisorSigma[2, n]; Array[a, 50] (* Amiram Eldar, Jul 31 2019 *)
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PROG
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(PARI) a(n) = sigma(n)^2 - sigma(n, 2); \\ Michel Marcus, Mar 22 2020
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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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