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 A094381 Number of numbers having exactly n representations as ab+ac+bc with 1 <= a <= b <= c. 4
 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; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS 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. REFERENCES See A025052 LINKS EXAMPLE a(1) = 16 because there are 16 numbers (A093670) with unique representations. MATHEMATICA 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}] CROSSREFS Cf. A025052 (n having no representations), A093670 (n having one representation), A094379, A094380. Sequence in context: A299557 A079293 A070646 * A074972 A118511 A022974 Adjacent sequences:  A094378 A094379 A094380 * A094382 A094383 A094384 KEYWORD nonn AUTHOR T. D. Noe, Apr 28 2004 STATUS approved

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Last modified February 21 23:41 EST 2020. Contains 332113 sequences. (Running on oeis4.)