A363938 Lexicographically earliest sequence of numbers in a hexagonal spiral such that their neighbors have no common prime factor.

1, 2, 3, 4, 5, 6, 7, 9, 11, 13, 8, 17, 15, 19, 12, 23, 25, 29, 10, 31, 14, 27, 16, 21, 37, 33, 26, 41, 22, 35, 43, 47, 18, 49, 24, 53, 39, 20, 51, 55, 28, 59, 61, 32, 45, 34, 67, 57, 40, 63, 71, 36, 65, 38, 73, 79, 30, 83, 77, 46, 89, 69, 91, 58, 81, 85, 87

Offset

1,2

Links

Carole Dubois, Table of n, a(n) for n = 1..4999

Carole Dubois, Hexagonal spiral for A363938.

Carole Dubois, Scatterplot of A363938(n)

Carole Dubois, Hexagons with spiral

Example

a(11) = 8 because the neighbors of the 11th hexagon are 3, 13, 17, 21, 33, 37, which do not have any common prime divisor with 8.

Crossrefs

Cf. A000384, A003458, A014105, A056105, A363765.

Sequence in context: A062490 A211543 A180711 * A032957 A362132 A210845

Adjacent sequences: A363935 A363936 A363937 * A363939 A363940 A363941

Keyword

nonn

Author

Carole Dubois, Jun 29 2023

Status

approved