OFFSET
1,2
COMMENTS
See A339228 for additional details.
EXAMPLE
In the following examples elements in series are juxtaposed and elements in parallel are separated by '|'.
a(1) = 1: (1).
a(2) = 5: (11), (12), (21), (1|1), (1|2).
PROG
(PARI) \\ See A339228 for R(n, k).
seq(n)={sum(k=1, n, R(n, k)*sum(r=k, n, binomial(r, k)*(-1)^(r-k)) )}
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Nov 28 2020
STATUS
approved