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A297792
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a(n) = Sum_{d|n} min(d, n/d)^2.
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5
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1, 2, 2, 6, 2, 10, 2, 10, 11, 10, 2, 28, 2, 10, 20, 26, 2, 28, 2, 42, 20, 10, 2, 60, 27, 10, 20, 42, 2, 78, 2, 42, 20, 10, 52, 96, 2, 10, 20, 92, 2, 100, 2, 42, 70, 10, 2, 132, 51, 60, 20, 42, 2, 100, 52, 140, 20, 10, 2, 182, 2, 10, 118, 106, 52, 100, 2, 42, 20
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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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a(p) = 2, for prime p.
a(2p) = 10, for odd prime p. (End)
a(r*p) = 2 + 2*r^2, where r, p are primes and p > r. - Bruno Berselli, Jan 09 2018
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MATHEMATICA
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a[n_] := Block[{d = Divisors@n}, Plus @@ (Min[#, n/#]^2 & /@ d)]; Array[a, 70] (* Robert G. Wilson v, Jan 06 2018 *)
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PROG
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(PARI) {a(n) = sumdiv(n, d, min(d, n/d)^2)}
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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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