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Search: id:A094378
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| A094378 |
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Number of numbers having exactly n representations as ab+ac+bc with 0 < a < b < c. |
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+0
4
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| 65, 23, 91, 40, 197, 39, 195, 56, 298, 87, 217, 60, 512, 97, 327, 77, 562, 125, 433, 88, 712, 125, 484, 115, 924, 121
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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Numbers up to 250,000 were checked. Note that there seem to be many more numbers having an even number of representations. Note that the Mathematica program computes A094376, A094377 and A094378, but outputs only this sequence.
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REFERENCES
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See A025052
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EXAMPLE
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a(1) = 23 because there are 23 numbers (A093669) with unique representations.
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MATHEMATICA
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cntMax=10; nSol=Table[{0, 0, 0}, {cntMax+1}]; Do[lim=Ceiling[(n-2)/3]; cnt=0; Do[If[n>a*b && Mod[n-a*b, a+b]==0 && Quotient[n-a*b, a+b]>b, cnt++; If[cnt>cntMax, Break[]]], {a, 1, lim-1}, {b, a+1, lim}]; If[cnt<=cntMax, If[nSol[[cnt+1, 1]]==0, nSol[[cnt+1, 1]]=n]; nSol[[cnt+1, 2]]=n; nSol[[cnt+1, 3]]++; ], {n, 10000}]; Table[nSol[[i, 3]], {i, cntMax+1}]
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CROSSREFS
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Cf. A000926 (n having no representations), A093669 (n having one representation), A094376, A094377.
Sequence in context: A087928 A034061 A113696 this_sequence A033385 A130764 A043625
Adjacent sequences: A094375 A094376 A094377 this_sequence A094379 A094380 A094381
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KEYWORD
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nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Apr 28 2004
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