A244818 The hexagonal spiral of Champernowne, read along the 120-degree ray.

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

Offset

1,3

Links

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

Formula

(12n^2-17n+6)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 - 17n + 6 (* see formula section of A244807 *); Array[ almostNatural[ f@#, 10] &, 105]

Crossrefs

Cf. A007376, A033577, A244807, A244808, A244809, A244810, A244811, A244812, A244813, A244814, A244815, A244816, A244817.

Sequence in context: A294644 A256128 A280501 * A244682 A201323 A155490

Adjacent sequences: A244815 A244816 A244817 * A244819 A244820 A244821

Keyword

nonn,easy

Author

Robert G. Wilson v, Jul 06 2014

Status

approved