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A137401
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a(n) is the number of ordered solutions (x,y,z) to x^3 + y^3 == z^3 mod n with 1 <= x,y,z <= n-1.
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2
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0, 0, 2, 7, 12, 20, 0, 63, 116, 72, 90, 131, 0, 108, 182, 339, 240, 602, 324, 415, 326, 420, 462, 839, 604, 216, 1808, 763, 756, 812, 810, 1735, 992, 1056, 1092, 3311, 648, 1620, 650, 2511, 1560, 1640, 1134, 2227, 4328, 1980, 2070, 3683, 2484, 2644, 2450, 1519
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Record values of A137401: 0, 2, 7, 12, 20, 63, 116, 131, 182, 339, 602, 839, 1808, 3311, 4328, 7964, 8864, 9231, 19583, 21986, 41363, 52676, 81467, 87596, 92087, 112616, 236951, 247940, 378071, 386423, 521135, .., . - Robert G. Wilson v.
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LINKS
| Robert G. Wilson v, Table of n, a(n) for n = 1..425..
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FORMULA
| a(n) = A063454(n)-3*A087786(n)+3*A000189(n)-1. - Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 11 2008
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EXAMPLE
| a(4)=7 because (1, 2, 1), (1, 3, 2), (2, 1, 1), (2, 2, 2), (2, 3, 3), (3, 1, 2), (3, 2, 3) are solutions for n=4.
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MATHEMATICA
| f[n_] := Block[ {c = 0}, Do[ If[ Mod[x^3 + y^3, n] == Mod[z^3, n], c++ ], {x, n - 1}, {y, n - 1}, {z, n - 1}]; c];
Table[Length[Select[Tuples[Range[n - 1], 3], Mod[ #[[1]]^3 + #[[2]]^3 - #[[3]]^3, n] == 0 &]], {n, 2, 50}] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 12 2008
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CROSSREFS
| Cf. A063454.
Sequence in context: A188039 A133459 A023669 * A119713 A135541 A180804
Adjacent sequences: A137398 A137399 A137400 * A137402 A137403 A137404
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KEYWORD
| nonn
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AUTHOR
| Neven Juric (neven.juric(AT)apis-it.hr), Apr 11, 2008
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EXTENSIONS
| More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com) and Robert G. Wilson v, (rgwv(AT)rgwv.com), Apr 12 2008
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