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A071692
Number of ways to write n as n = x! + y! + z! where 0<=x<=y<=z<=n.
1
0, 0, 0, 4, 3, 2, 1, 0, 3, 2, 1, 0, 0, 2, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 3, 2, 1, 0, 0, 2, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0
OFFSET
0,4
COMMENTS
If a(n) > 1 then a(n+1) = a(n) - 1.
If A034968(n) > 3 then a(n) = 0. - David A. Corneth, Jul 27 2015
LINKS
MAPLE
M:= 5: # for a(0) to a((M+1)!-1), where M >= 3
N:= (M+1)!-1:
A:= Array(0..N):
for x from 0 to M do for y from x to M do for z from y to M do
r:= x!+y!+z!;
A[r]:= A[r]+1;
od od od:
seq(A[i], i=0..N); # Robert Israel, Jul 27 2015
PROG
(PARI) for(n=1, 80, print1(sum(a=0, n, sum(b=0, a, sum(c=0, b, if(a!+b!+c!-n, 0, 1)))), ", "))
(PARI) a(n) = {my(f=1, t=0); while((f+1)!<=n, f++); forvec(u=vector(3, i, [0, f]), t+=(sum(i=1, 3, u[i]!)==n), 1); t} \\ David A. Corneth, Jul 27 2015
CROSSREFS
Cf. A034968.
Sequence in context: A258447 A066440 A182425 * A307335 A030586 A249345
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Jun 23 2002
EXTENSIONS
a(0)=0 prepended by David A. Corneth, Jul 28 2015
STATUS
approved