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 A308685 The number of triangular lattice points whose Euclidean distance from the origin is less than or equal to n. 1
 1, 7, 19, 37, 61, 91, 127, 187, 241, 301, 367, 439, 517, 613, 721, 823, 931, 1045, 1165, 1303, 1459, 1615, 1765, 1921, 2083, 2263, 2455, 2653, 2857, 3055, 3259, 3481, 3697, 3949, 4195, 4447, 4693, 4957, 5239, 5527, 5815, 6109, 6409, 6715, 7015, 7333, 7681 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Also the sum of the first n^2+1 terms of A004016. LINKS Peter Kagey, Table of n, a(n) for n = 0..1000 Code Golf Stack Exchange, Triangular Lattice Points close to the Origin FORMULA a(n) = A053416(2*n). CROSSREFS Cf. A004016, A053416. Sequence in context: A023224 A113743 A003215 * A133323 A002407 A098484 Adjacent sequences:  A308682 A308683 A308684 * A308686 A308687 A308688 KEYWORD nonn AUTHOR Peter Kagey, Jun 28 2019 STATUS approved

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Last modified April 21 01:35 EDT 2021. Contains 343143 sequences. (Running on oeis4.)