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A100438
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Number of distinct products i*j*k*l for 1 <= i < j < k < l <= n.
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1
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0, 0, 0, 1, 5, 13, 29, 50, 79, 111, 186, 219, 345, 428, 513, 610, 884, 991, 1387, 1535, 1742, 1994, 2671, 2833, 3319, 3719, 4154, 4474, 5751, 5985, 7575, 8121, 8803, 9593, 10401, 10785, 13303, 14371, 15414, 15988, 19379, 20089, 24103, 25237, 26369
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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MAPLE
| f:=proc(n) local i, j, k, l, t1; t1:={}; for i from 1 to n-3 do for j from i+1 to n-2 do for k from j+1 to n-1 do for l from k+1 to n do t1:={op(t1), i*j*k*l}; od: od: od: od: t1:=convert(t1, list); nops(t1); end;
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MATHEMATICA
| f[n_] := Length[ Union[ Flatten[ Table[ i*j*k*l, {i, n}, {j, i + 1, n}, {k, j + 1, n}, {l, k + 1, n}]]]]; Table[ f[n], {n, 45}] (from Robert G. Wilson v Dec 14 2004)
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CROSSREFS
| Cf. A027425, A027430, A100435, A100436, A100437.
Sequence in context: A095085 A093836 A000328 * A129371 A194270 A194700
Adjacent sequences: A100435 A100436 A100437 * A100439 A100440 A100441
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Nov 21 2004
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 14 2004
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