A368103 a(1)=1; for n>1, a(n) is the smallest number not already used which has a factor difference in common with a(n-1).
1, 4, 9, 16, 7, 27, 40, 10, 18, 8, 3, 15, 24, 6, 2, 12, 5, 21, 32, 45, 13, 28, 54, 26, 42, 20, 30, 14, 36, 17, 57, 80, 35, 48, 23, 75, 11, 39, 56, 72, 22, 46, 94, 144, 19, 63, 88, 43, 135, 55, 91, 112, 25, 49, 64, 31, 99, 120, 38, 60, 29, 93, 128, 33, 65, 84, 41, 129, 176, 50, 66, 92, 141, 192
Offset: 1
Keywords
Examples
For n=2, a(1)=1 can be factored only as 1*1, which has difference 0. The next term cannot be 2 and 3 as they do not have a factor difference 0, but 4 = 2*2 does, so that a(2) = 4. For n=5, a(4)=16 has factor differences 0,6,15 and the smallest unused number with one of those differences is a(5) = 7 = 7*1 difference 6.
Links
- Neal Gersh Tolunsky, Table of n, a(n) for n = 1..10000
- Thomas Scheuerle, MATLAB Script.
- Thomas Scheuerle, Plot of the first 393 prime numbers over their indices of appearance. It is remarkable that prime numbers do not appear in order.
Programs
-
MATLAB
% See Scheuerle link.
Comments