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A195030
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a(n) = (n-2)*(14*n-39) for n > 2, otherwise a(n) = n.
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4
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0, 1, 2, 3, 34, 93, 180, 295, 438, 609, 808, 1035, 1290, 1573, 1884, 2223, 2590, 2985, 3408, 3859, 4338, 4845, 5380, 5943, 6534, 7153, 7800, 8475, 9178, 9909, 10668, 11455, 12270, 13113, 13984, 14883, 15810, 16765, 17748, 18759, 19798, 20865, 21960, 23083
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OFFSET
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0,3
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COMMENTS
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Sequence found by reading the line from 0, in the direction 0, 1,..., in the Pythagorean spiral whose edges have length A195019 and whose vertices are the numbers A195020. This is the one of the semi-axis of the square spiral, which is related to the primitive Pythagorean triple [3, 4, 5].
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LINKS
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FORMULA
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MATHEMATICA
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Join[{0, 1, 2}, Table[(n-2)*(14*n-39), {n, 3, 50}]] (* Vincenzo Librandi, Jul 10 2012
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PROG
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(Magma) [0, 1, 2] cat[(n-2)*(14*n-39): n in [3..50]]; // Vincenzo Librandi, Jul 10 2012
(PARI) a(n)=if(n, ([0, 1, 0; 0, 0, 1; 1, -3, 3]^n*[0; 1; 2])[1, 1], 0) \\ Charles R Greathouse IV, Oct 16 2015
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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