A370500 a(1) = 1, a(2) = 2; for n > 2, a(n) is the smallest unused positive number such that a(n) does not share a factor with a(n-1) but sopfr(a(n)) does share a factor with soprf(a(n-1)), where sopfr(k) is the sum of the primes dividing k, with repetition.
1, 2, 9, 4, 15, 8, 3, 14, 27, 20, 77, 16, 21, 5, 6, 25, 18, 35, 24, 65, 32, 33, 7, 10, 49, 12, 115, 36, 55, 39, 50, 51, 26, 81, 38, 105, 44, 91, 30, 119, 57, 11, 28, 45, 62, 85, 42, 95, 64, 69, 13, 22, 63, 74, 75, 56, 169, 60, 121, 40, 123, 70, 87, 98, 93, 17, 52, 99, 145, 66, 133, 72, 125, 46
Offset: 1
Keywords
Examples
a(4) = 4 as a(3) = 9 and 4 does not share a factor with 9 while sopfr(4) = 4 does share a factor with sopfr(9) = 6.
Links
- Scott R. Shannon, Table of n, a(n) for n = 1..10000
Comments