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A143839
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Ulam's spiral (SSE spoke).
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4
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1, 24, 79, 166, 285, 436, 619, 834, 1081, 1360, 1671, 2014, 2389, 2796, 3235, 3706, 4209, 4744, 5311, 5910, 6541, 7204, 7899, 8626, 9385, 10176, 10999, 11854, 12741, 13660, 14611, 15594, 16609, 17656, 18735, 19846, 20989, 22164, 23371, 24610
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OFFSET
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1,2
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COMMENTS
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Also sequence found by reading the line from 1, in the direction 1, 24, ... in the square spiral whose vertices are the generalized decagonal numbers A074377. - Omar E. Pol, Nov 05 2012
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LINKS
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FORMULA
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a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3); a(1) = 1, a(2) = 24, a(3) = 79. - Harvey P. Dale, May 26 2012
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MAPLE
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seq( ((32*n -25)^2 +15)/64, n=1..40); # G. C. Greubel, Nov 09 2019
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MATHEMATICA
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LinearRecurrence[{3, -3, 1}, {1, 24, 79}, 40] (* Harvey P. Dale, May 26 2012 *)
CoefficientList[Series[(1+21*x+10*x^2)/(1-x)^3, {x, 0, 40}], x] (* Vincenzo Librandi, Nov 08 2014 *)
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PROG
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(PARI) Vec(x*(1+21*x+10*x^2)/(1-x)^3 + O(x^40)) \\ Colin Barker, Nov 08 2014
(Sage) [((32*n -25)^2 +15)/64 for n in (1..40)] # G. C. Greubel, Nov 09 2019
(GAP) List([1..40], n-> ((32*n -25)^2 +15)/64); # G. C. Greubel, Nov 09 2019
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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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STATUS
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approved
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