OFFSET
0,3
COMMENTS
A003107 & this sequence are different sequences. A003107 gives the number of partitions in which each part of n is a Fibonacci number, this sequence gives the number of partitions in which the number of parts is a Fibonacci number. Both sequences share the same values for the first 9 values. For example A003107(4) = 4 because of the following 4 partitions of 5: (3,1), (2,2), (2,1,1), (1,1,1,1) whereas a(4) is also 4 but because of different set of partitions: (4), (3,1), (2,2), (2,1,1).
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..5000
FORMULA
G.f.: 1 + Sum_{n>=2} x^Fibonacci(n)/Product_{i=1..Fibonacci(n)} (1-x^i). - Vladeta Jovovic, Mar 02 2005
EXAMPLE
a(5) = 6 since out of 7 possible partitions of 5 into integer parts, only 6 include a Fibonacci number of parts: (5), (4,1), (3,2), (3,1,1), (2,2,1), (1,1,1,1,1). The 7th integer partitions of 5 (2,1,1,1) is not counted since it includes 4 integer parts and 4 is not a Fibonacci number.
MAPLE
b:= proc(n, i, t) option remember; `if`(n=0 or i=1,
`if`((h-> issqr(h+4) or issqr(h-4))(5*(t+n)^2), 1, 0),
b(n, i-1, t) + b(n-i, min(i, n-i), t+1))
end:
a:= n-> b(n$2, 0):
seq(a(n), n=0..80); # Alois P. Heinz, Jul 29 2017
MATHEMATICA
b[n_, i_, t_] := b[n, i, t] = If[n == 0 || i == 1, If[IntegerQ @ Sqrt[# + 4] || IntegerQ @ Sqrt[# - 4]&[5*(t + n)^2], 1, 0], b[n, i - 1, t] + b[n - i, Min[i, n - i], t + 1]];
a[n_] := b[n, n, 0];
Table[a[n], {n, 0, 80}] (* Jean-François Alcover, May 20 2018, after Alois P. Heinz *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Lior Manor, Feb 28 2005
EXTENSIONS
More terms from Vladeta Jovovic, Mar 02 2005
a(0)=1 prepended by Alois P. Heinz, Jul 29 2017
STATUS
approved