a(n) = (1/5)*(4 + Sum_{k=0..n} C(5*k,k)).
A024721
a(n) = (1/5)*(4 + Sum_{k=0..n} C(5*k,k)).
Terms
- a(0) =1a(1) =2a(2) =11a(3) =102a(4) =1071a(5) =11697a(6) =130452a(7) =1475356a(8) =16856293a(9) =194088920a(10) =2248544554a(11) =26179257724a(12) =306051026719
External references
- oeis: A024721