OFFSET
1,3
REFERENCES
D. E. Knuth: The Art of Computer Programming, Volume 4, Generating All Combinations and Partitions Fascicle 3, Section 7.2.1.4. Generating all partitions. Page 38, Algorithm H.
FORMULA
a(n) = Sum of prod_{k=1..n} C(A035053(k)+c_k-1,c_k}) over the partitions of n having all parts k prime, c_1 + 2c_2 + ... + nc_n; c_1, c_2, ..., c_n >= 0.
EXAMPLE
a(5) = 11 since the only options are 9 hypertrees of order 5, or the two hyperforests composed by components of order 3 and 2.
CROSSREFS
KEYWORD
nonn
AUTHOR
Washington Bomfim, Sep 28 2008
STATUS
approved