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A363938
Lexicographically earliest sequence of numbers in a hexagonal spiral such that their neighbors have no common prime factor.
1
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
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
KEYWORD
nonn
AUTHOR
Carole Dubois, Jun 29 2023
STATUS
approved