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 A212101 Number of (w,x,y,z) with all terms in {1,...,n} and w*x^2=y*z^2. 2
 0, 1, 4, 9, 20, 29, 42, 55, 80, 109, 132, 153, 196, 221, 254, 287, 356, 389, 460, 497, 568, 617, 670, 715, 808, 897, 960, 1057, 1156, 1213, 1306, 1367, 1512, 1589, 1672, 1749, 1964, 2037, 2130, 2223, 2376, 2457, 2580, 2665, 2824, 2997, 3110 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS For a guide to related sequences, see A211795. LINKS Table of n, a(n) for n=0..46. EXAMPLE The four (w,x,y,z) counted by a(2): (1,1,1,1), (1,2,1,2), (2,1,2,1), (2,2,2,2). MATHEMATICA t = Compile[{{n, _Integer}}, Module[{s = 0}, (Do[If[w*x^2 == y*z^2, s = s + 1], {w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]]; Map[t[#] &, Range[0, 60]] (* A212101 *) (* Peter J. C. Moses, Apr 13 2012 *) CROSSREFS Cf. A211795. Sequence in context: A066109 A030734 A368587 * A073360 A297190 A075385 Adjacent sequences: A212098 A212099 A212100 * A212102 A212103 A212104 KEYWORD nonn AUTHOR Clark Kimberling, May 03 2012 STATUS approved

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Last modified June 12 17:51 EDT 2024. Contains 373359 sequences. (Running on oeis4.)