OFFSET
0,2
COMMENTS
a(0) = 1 corresponds to the empty sum, in which all terms are colored in one among two given colors, since there is no term at all.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..50
OEIS wiki: Plane partitions
Wikipedia, Plane partition
FORMULA
a(n) = Sum_{k=1..n} A091298(n,k)*2^k.
EXAMPLE
For n = 1, there is only the partition [1], which can be colored in any of the two colors, whence a(1) = 2.
For n = 2, there are the partitions [2], [1,1] and [1;1]. Adding colors, this yields a(2) = 2 + 4 + 4 = 10 distinct possibilities.
PROG
(PARI) a(n)=!n+sum(k=1, n, A091298(n, k)<<k)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(12) corrected and a(13)-a(28) added by Alois P. Heinz, Sep 24 2018
STATUS
approved