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A158057
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First differences of A051870: 16*n + 1.
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18
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1, 17, 33, 49, 65, 81, 97, 113, 129, 145, 161, 177, 193, 209, 225, 241, 257, 273, 289, 305, 321, 337, 353, 369, 385, 401, 417, 433, 449, 465, 481, 497, 513, 529, 545, 561, 577, 593, 609, 625, 641, 657, 673, 689, 705, 721, 737, 753, 769, 785, 801, 817, 833, 849
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OFFSET
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0,2
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COMMENTS
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The identity (16*n+1)^2 - (16*n^2+2*n)*(4)^2 = 1 can be written as a(n+1)^2 - A158056(n)*(4)^2 = 1. - Vincenzo Librandi, Feb 09 2012
This sequence gives the 18-gonal (or octadecagonal) gnomonic numbers. Name suggested by Todd Silvestri, Nov 22 2014
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LINKS
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FORMULA
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a(n) = 16*n + 1.
a(n) = 2*a(n-1) - a(n-2), a(0) = 1, a(1) = 17.
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MAPLE
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MATHEMATICA
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LinearRecurrence[{2, -1}, {1, 17}, 60]
CoefficientList[Series[(1+15x)/(1-x)^2, {x, 0, 60}], x] (* Vincenzo Librandi, Nov 23 2014 *)
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PROG
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(Magma) I:=[1, 17]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]];
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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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Edited: Offset changed to 0 according to the
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STATUS
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approved
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