OFFSET
1,1
FORMULA
A027480(k) = k * (k + 1) * (k + 2) / 2 is in the sequence for k >= 2.
EXAMPLE
There are 30 permutations of 5 balls where 2 are red, 2 are yellow and 1 is blue.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
David A. Corneth, May 24 2018
STATUS
approved