A359663 a(1) = 1; for n > 1, a(n) is the smallest positive number which has not appeared that shares a factor with the sum of the first n terms of the Champernowne string starting from 1.
1, 3, 2, 4, 5, 6, 7, 8, 9, 10, 12, 47, 14, 21, 15, 13, 11, 16, 18, 61, 20, 67, 73, 22, 24, 26, 25, 28, 30, 17, 27, 32, 33, 107, 109, 36, 19, 29, 34, 38, 127, 39, 35, 137, 40, 42, 44, 45, 48, 46, 49, 51, 43, 50, 54, 52, 57, 31, 55, 193, 56, 60, 23, 58, 62, 64, 63, 66, 65, 68, 70, 72, 69, 77, 75, 37
Offset: 1
Examples
a(3) = 2 as the sum of the first 3 terms of the Champernowne string is 1 + 2 + 3 = 6, and 2 is the smallest unused number that shares a factor with 6. a(10) = 10 as the sum of the first 10 terms of the Champernowne string is 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 1 = 46, and 10 is the smallest unused number that shares a factor with 46.
Links
- Scott R. Shannon, Image of the first 100000 terms. The green line is a(n) = n.
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