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A331449
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a(0) = 1 by convention; for n>0, a(n) is the number of points in the n-th figure shown in A255011 (meaning the figure with 4n points on the perimeter).
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11
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1, 5, 37, 257, 817, 2757, 4825, 12293, 19241, 33549, 49577, 87685, 101981, 178465, 220113, 286357, 379097, 551669, 606241, 880293, 951445, 1209049, 1507521, 1947877, 2002669, 2624409, 3056093, 3550425, 3955049, 5069037, 5062153, 6669665, 7081969, 8143193, 9365089, 10296469
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OFFSET
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0,2
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COMMENTS
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Equivalently, this is A334690(n) + 4*n.
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LINKS
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Lars Blomberg, Table of n, a(n) for n = 0..52
Lars Blomberg, Scott R. Shannon, and N. J. A. Sloane, Graphical Enumeration and Stained Glass Windows, 1: Rectangular Grids, (2021). Also arXiv:2009.07918.
N. J. A. Sloane, "A Handbook of Integer Sequences" Fifty Years Later, arXiv:2301.03149 [math.NT], 2023, p. 20.
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FORMULA
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By Euler's formula, a(n) = A331448(n) - A255011(n) + 1.
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CROSSREFS
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Cf. A255011, A331448.
For the circular analog see A006533, A007678, A007569, A135565.
Sequence in context: A080507 A108049 A121141 * A220634 A083232 A236581
Adjacent sequences: A331446 A331447 A331448 * A331450 A331451 A331452
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, Jan 23 2020
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EXTENSIONS
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a(11)-a(35) from Giovanni Resta, Jan 28 2020
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STATUS
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approved
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