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Search: id:A094381
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| A094381 |
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Number of numbers having exactly n representations as ab+ac+bc with 1 <= a <= b <= c. |
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+0
4
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| 18, 16, 61, 30, 133, 51, 119, 48, 275, 59, 217, 72, 386, 65, 292, 83, 545, 101, 332, 89, 673, 120, 453, 106, 865, 104
(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 A094379, A094380, and A094381, 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) = 16 because there are 16 numbers (A093670) 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-1)/2]; 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}, {b, a, 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. A025052 (n having no representations), A093670 (n having one representation), A094379, A094380.
Adjacent sequences: A094378 A094379 A094380 this_sequence A094382 A094383 A094384
Sequence in context: A077668 A079293 A070646 this_sequence A074972 A118511 A022974
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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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