a(1)=1; a(n)=sum(u=1,n-1,sum(v=1,u,sum(w=1,v,sum(x=1, w,sum(y=1,x,a(y)))))).

A079675

a(1)=1; a(n)=sum(u=1,n-1,sum(v=1,u,sum(w=1,v,sum(x=1, w,sum(y=1,x,a(y)))))).

Terms

    a(0) =1a(1) =1a(2) =6a(3) =26a(4) =106a(5) =431a(6) =1757a(7) =7168a(8) =29244a(9) =119305a(10) =486716a(11) =1985603a(12) =8100456a(13) =33046585a(14) =134816705a(15) =549997641a(16) =2243767969a(17) =9153665985a(18) =37343255690a(19) =152345382480a(20) =621507555626

External references