OFFSET
1,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..600
W. C. Yang, Derivatives are essentially integer partitions, Discrete Mathematics, 222(1-3), July 2000, 235-245.
FORMULA
a(n) ~ c * d^n / sqrt(n), where d = A270915 = 5.35270133348664..., c = 0.0504640078963302151598181537452... . - Vaclav Kotesovec, Sep 03 2014, updated May 19 2018
MAPLE
A:= proc(n, k) option remember;
`if`(k=1, 1, add(b(n, n, i)*A(i, k-1), i=0..n))
end:
b:= proc(n, i, k) option remember; `if`(n<k, 0, `if`(n=0, 1, `if`(i<1, 0,
`if`(n=k, 1, add(b(n-i*j, i-1, k-j), j=0..min(n/i, k))))))
end:
a:= n-> A(n, n):
seq(a(n), n=1..40);
MATHEMATICA
A[n_, k_] := A[n, k] = If[k == 1, 1, Sum[b[n, n, i]*A[i, k-1], {i, 0, n}]]; b[n_, i_, k_] := b[n, i, k] = If[n<k, 0, If[n == 0, 1, If[i<1, 0, If[n == k, 1, Sum[b[n - i*j, i-1, k-j], {j, 0, Min[n/i, k]}]]]]]; a[n_] := A[n, n]; Table[a[n], {n, 1, 40}] (* Jean-François Alcover, Feb 05 2015, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 18 2012
STATUS
approved