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Search: id:A121509
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| 1, 3, 11, 23, 41, 63, 91, 123, 161, 203, 251, 303, 361, 423, 491, 563, 641, 723, 811, 903, 1001, 1103, 1211, 1323, 1441, 1563, 1691, 1823, 1961, 2103
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Geometrically, it starts as a square of points followed by a switch to hexagon of points.
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FORMULA
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M := {{0, 1}, {-1, 2} } v[1] = {1, 7} w[n_] = If[Mod[n, 2] == 0, {0, 4}, {0, 6}] v[n_] := v[n] = M.v[n - 1] + w[n] a(n) = v[n][[1]]
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MATHEMATICA
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M := {{0, 1}, {-1, 2} } v[1] = {1, 7} w[n_] = If[Mod[n, 2] == 0, {0, 4}, {0, 6}] v[n_] := v[n] = M.v[n - 1] + w[n] a = Table[v[n][[1]], {n, 1, 30}]
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CROSSREFS
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Cf. A003215, A005448, A001849.
Adjacent sequences: A121506 A121507 A121508 this_sequence A121510 A121511 A121512
Sequence in context: A106201 A132209 A086497 this_sequence A096071 A078723 A141187
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KEYWORD
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nonn,uned
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AUTHOR
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Roger Bagula (rlbagulatftn(AT)yahoo.com), Sep 07 2006
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