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Search: id:A071954
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| A071954 |
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a(n) = 4*a(n-1) - a(n-2) - 4, with a(0)=2, a(1)=4. |
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+0
5
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| 2, 4, 10, 32, 114, 420, 1562, 5824, 21730, 81092, 302634, 1129440, 4215122, 15731044, 58709050, 219105152, 817711554, 3051741060, 11389252682, 42505269664, 158631825970, 592022034212, 2209456310874, 8245803209280
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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a(n) gives the side of a cube having a square number of cubes in its two outermost layers, i.e. solutions p to the equation p^3 - (p-4)^3 = q^2. The corresponding q is given by 4*A001075(n).
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REFERENCES
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M. E. Larsen, "Four Cubes" in Puzzler's Tribute, Ed. D. Wolfe & T. Rodgers, pp. 69-70, A. K. Peters, MA, 2002
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MATHEMATICA
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a[n_] := a[n] = 4*a[n - 1] - a[n - 2] - 4; a[0] = 2; a[1] = 4; Table[ a[n], {n, 0, 25}]
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CROSSREFS
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Equals A052530(n) + 2, n>0. Cf. A003699.
Sequence in context: A005268 A005269 A070900 this_sequence A120017 A000736 A001250
Adjacent sequences: A071951 A071952 A071953 this_sequence A071955 A071956 A071957
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KEYWORD
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nice,nonn
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AUTHOR
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Lekraj Beedassy (blekraj(AT)yahoo.com), Jun 25 2002
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EXTENSIONS
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Edited by Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 27 2002
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