Number of sequences of balls colored with at most n colors such that exactly two balls are of a color seen earlier in the sequence.
A281946
Number of sequences of balls colored with at most n colors such that exactly two balls are of a color seen earlier in the sequence.
Terms
- a(0) =1a(1) =16a(2) =195a(3) =2248a(4) =26245a(5) =318936a(6) =4082071a(7) =55289200a(8) =793525833a(9) =12063384640a(10) =194002619371
External references
- oeis: A281946