A071691 - OEIS

%I #6 Mar 30 2012 18:39:02

%S 0,0,0,5,4,3,2,1,4,3,2,1,0,3,2,1,0,0,2,1,0,0,0,1,0,0,4,3,2,1,0,3,2,1,

%T 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,

%U 0,0,0,0,2,1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0

%N Number of ways to write n as n = x!+y!+z!+t! with 0<=x<=y<=z<=t<=n.

%C If a(n) > 1, a(n+1) = a(n) - 1.

%C Since numbers of the form n! are rare, sequence behaves quite regularly. - Lambert Klasen (lambert.klasen(AT)gmx.de), Dec 23 2004

%o (PARI) for(n=1,54,print1(sum(a=0,n,sum(b=0,a,sum(c=0,b,sum(d=0,c,if(a!+b!+c!+d!-n,0,1))))),","))

%K easy,nonn

%O 1,4

%A _Benoit Cloitre_, Jun 23 2002

%E More terms from Lambert Klasen (lambert.klasen(AT)gmx.de), Dec 23 2004