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 A309407 a(n) = round(sqrt(3*n + 9/4)), with a(0) = 1. 2
 1, 2, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, 16, 16 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Diverges from A046693 at positions in A308766. For the first 1750 terms, A046693(n)-a(n) is either 0 or 1. LINKS Ed Pegg Jr, Sparse Rulers. FORMULA a(n) = round(sqrt(3*n + 9/4)). MATHEMATICA Table[If[n == 0, 1, Round[Sqrt[3 n + 9/4]]], {n, 0, 88}] CROSSREFS Cf. A046693, A308766, A326499. Sequence in context: A003057 A239308 A216256 * A046693 A196376 A156077 Adjacent sequences:  A309404 A309405 A309406 * A309408 A309409 A309410 KEYWORD nonn,easy AUTHOR Ed Pegg Jr, Jul 29 2019 STATUS approved

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Last modified December 5 22:37 EST 2019. Contains 329782 sequences. (Running on oeis4.)