OFFSET
1,3
COMMENTS
a(n) is also the number of weak compositions of n into n parts in which at least one part is zero and the composition does not contain a single nonzero part.
FORMULA
EXAMPLE
a(4)=30 since 4 can be written as 3+1+0+0, 0+3+1+0, etc. (12 such compositions); 2+2+0+0 (6 such compositions); 2+1+1+0 (12 such compositions).
CROSSREFS
KEYWORD
nonn
AUTHOR
Enrique Navarrete, Mar 08 2024
STATUS
approved