A378098 Lexicographically earliest sequence of distinct positive integers such that a(a(n)) shares a factor with a(a(n)-1).
2, 4, 5, 10, 6, 8, 9, 12, 14, 16, 13, 26, 18, 15, 20, 22, 19, 38, 24, 21, 27, 30, 25, 35, 28, 32, 34, 36, 23, 46, 33, 39, 42, 40, 44, 48, 41, 82, 50, 45, 51, 54, 47, 94, 52, 56, 49, 63, 57, 60, 55, 65, 58, 62, 64, 66, 68, 70, 61, 122, 72, 69, 75, 78, 74, 76, 71, 142, 80, 84, 77, 88, 79, 158, 86, 90, 81, 87, 93, 96, 92, 98, 85, 95, 100, 102, 99, 105, 91, 104
Offset: 1
Keywords
Examples
a(2) = 4 as a(1) = 2 and 4 is the smallest unused number that shares a factor with a(2-1) = a(1) = 2. a(3) = 5 as a(3) is not referenced earlier in the sequence so it is the lowest unused number that does not violate the sharing factor requirement. It cannot be 3 as that would require a(3) = 3 to share a factor with a(3-1) = a(2) = 4, which is does not, and it cannot be 4 as that has already been used.
Links
- Scott R. Shannon, Table of n, a(n) for n = 1..10000
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