A244814 The hexagonal spiral of Champernowne, read along the 240-degree ray.

1, 1, 2, 6, 1, 1, 1, 2, 3, 3, 4, 5, 6, 7, 8, 9, 7, 5, 2, 1, 2, 1, 7, 1, 3, 7, 3, 2, 0, 2, 0, 3, 3, 6, 7, 3, 2, 1, 6, 4, 7, 5, 6, 5, 8, 8, 6, 6, 5, 1, 8, 8, 8, 4, 0, 9, 7, 1, 3, 1, 0, 1, 1, 8, 1, 2, 2, 1, 6, 1, 4, 4, 1, 5, 1, 5, 6, 1, 7, 1, 7, 8, 1, 0, 1, 9, 0, 2, 6, 2, 1, 2, 2, 3, 2, 3, 4, 2, 3, 2, 6, 6, 2, 4, 2

Offset

1,3

Links

Table of n, a(n) for n=1..105.

Formula

(12n^2 - 21n + 10)th almost natural number (A033307), Also see formula section of A056105.

Example

see A244807 example section for its diagram.

Mathematica

almostNatural[n_, b_] := Block[{m = 0, d = n, i = 1, l, p}, While[m <= d, l = m; m = (b - 1) i*b^(i - 1) + l; i++]; i--; p = Mod[d - l, i]; q = Floor[(d - l)/i] + b^(i - 1); If[p != 0, IntegerDigits[q, b][[p]], Mod[q - 1, b]]]; f[n_] := 12n^2 - 21n + 10 (* see formula section of A244807 *); Array[ almostNatural[ f@#, 10] &, 105]

Crossrefs

Cf. A007376, A244805, A244807, A244808, A244809, A244810, A244811, A244812, A244813, A244815, A244816, A244817, A244818.

Sequence in context: A021387 A321172 A127508 * A090185 A059813 A097099

Adjacent sequences: A244811 A244812 A244813 * A244815 A244816 A244817

Keyword

nonn,easy

Author

Robert G. Wilson v, Jul 06 2014

Status

approved