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A169953
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Third entry in row n of triangle in A169950.
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1
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1, 1, 4, 8, 15, 23, 44, 64, 117, 173, 262, 374, 571, 791, 1188, 1644, 2355, 3205, 4552, 5980, 8283, 10925, 14702, 19338, 26031, 33581, 44690, 57566, 75531, 96531, 125738, 158690, 204953, 258325, 329394, 412054, 523931, 649973, 822434, 1018332, 1274909
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OFFSET
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2,3
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COMMENTS
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Wanted: a recurrence. Are any of A169940-A169954 related to any other entries in the OEIS?
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LINKS
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FORMULA
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MATHEMATICA
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b[n_, s_] := b[n, s] = Module[{sn, m}, m = Length[s]; sn = Append[s, n]; If[n < 1, 1, b[n - 1, s] + If[m*(m + 1)/2 == Length[Union[Flatten[Table[ sn[[i]] + sn[[j]], {i, 1, m}, {j, i + 1, m + 1}]]]], b[n - 1, sn], 0]]];
A196723[n_] := A196723[n] = b[n - 1, {n}] + If[n == 0, 0, A196723[n - 1]]; c[n_, s_] := c[n, s] = Module[{sn, m}, If[n < 1, 1, sn = Append[s, n]; m = Length[sn]; If[m*(m - 1)/2 == Length[Table[sn[[i]] - sn[[j]], {i, 1, m - 1}, {j, i + 1, m}] // Flatten // Union], c[n-1, sn], 0] + c[n-1, s]]];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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