A285493 a(n) is the least positive integer not already appearing such that no two distinct unordered pairs of points ((n, a(n)), (m, a(m))) and ((k, a(k)), (j, a(j))) have the same midpoint.
1, 2, 4, 3, 6, 10, 15, 5, 13, 9, 18, 29, 7, 25, 37, 8, 22, 14, 41, 48, 23, 58, 11, 66, 32, 78, 24, 52, 83, 12, 73, 93, 26, 60, 42, 118, 21, 89, 65, 106, 139, 145, 19, 84, 16, 162, 76, 43, 173, 183, 199, 123, 87, 30, 28, 161, 101, 56, 116, 55, 235, 182, 150
Offset: 1
Examples
a(3) != 3 or else midpoint((3,3), (1,1)) = midpoint((2,2), (2,2)), thus a(3) = 4. a(6) != 5 or else midpoint((6,5), (3,4)) = midpoint((4,3), (5,6)); a(6) != 7 or else midpoint((6,7), (1,1)) = midpoint((2,2), (5,6)); a(6) != 8 or else midpoint((6,8), (2,2)) = midpoint((3,4), (5,6)); a(6) != 9 or else midpoint((6,9), (4,3)) = midpoint((5,6), (5,6)); thus a(6) = 10.
Links
- Giovanni Resta, Table of n, a(n) for n = 1..3000 (first 650 terms from Peter Kagey)
Comments