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A087694
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Number of non-congruent solutions to x^2 + xy + y^2 = 0 mod n.
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2
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1, 1, 3, 4, 1, 3, 13, 4, 9, 1, 1, 12, 25, 13, 3, 16, 1, 9, 37, 4, 39, 1, 1, 12, 25, 25, 27, 52, 1, 3, 61, 16, 3, 1, 13, 36, 73, 37, 75, 4, 1, 39, 85, 4, 9, 1, 1, 48, 133, 25, 3, 100, 1, 27, 1, 52, 111, 1, 1, 12, 121, 61, 117, 64, 25, 3, 133, 4, 3, 13
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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FORMULA
| Multiplicative with a(3^e) = 3^e, a(p^e) = ((p-1)*e+p)*p^(e-1) if p mod 3 = 1, a(p^e) = p^(2*floor(e/2)) if p mod 3 = 2. - Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 27 2003
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MAPLE
| A087694 := proc(n) option remember; local pf, p, f, e ; if n = 1 then 1; else pf := ifactors(n)[2] ; if nops(pf) = 1 then f := op(1, pf) ; p := op(1, f) ; e := op(2, f) ; if p = 3 then n ; elif p mod 3 =1 then ((p-1)*e+p)*p^(e-1) ; else p^(2*floor(e/2)) ; end if; else mul(procname(op(1, p)^op(2, p)), p=pf) ; end if; end if; end proc:
seq(A087694(n), n=1..70) ; # R. J. Mathar, Jan 07 2011
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CROSSREFS
| Cf. A000086.
Sequence in context: A169782 A131228 A131129 * A010262 A201516 A105579
Adjacent sequences: A087691 A087692 A087693 * A087695 A087696 A087697
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KEYWORD
| mult,nonn
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AUTHOR
| Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 27 2003
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