A370501 a(1) = 1, a(2) = 2; for n > 2, a(n) is the smallest unused positive number such that a(n) shares a factor with a(n-1) but sopfr(a(n)) does not share a factor with soprf(a(n-1)), where sopfr(k) is the sum of the primes dividing k, with repetition.
1, 2, 6, 3, 12, 4, 10, 5, 15, 20, 16, 14, 7, 21, 24, 18, 22, 8, 28, 26, 13, 39, 27, 30, 34, 17, 51, 45, 9, 48, 32, 38, 19, 57, 63, 33, 11, 44, 40, 25, 75, 35, 56, 36, 52, 42, 46, 23, 69, 54, 50, 58, 29, 87, 90, 55, 80, 60, 76, 62, 31, 93, 96, 64, 82, 41, 123, 99, 66, 68, 85, 105, 49, 112
Offset: 1
Keywords
Examples
a(6) = 4 as a(5) = 12 and 4 shares a factor with 12 while sopfr(4) = 4 does not share a factor with sopfr(12) = 7.
Links
- Scott R. Shannon, Table of n, a(n) for n = 1..10000
Comments