a(n) = (1/n) * Sum_{i=0..n-1} C(n,i)*C(n,i+1)*3^i*4^(n-i), a(0)=1.
A103211
a(n) = (1/n) * Sum_{i=0..n-1} C(n,i)*C(n,i+1)*3^i*4^(n-i), a(0)=1.
Terms
- a(0) =1a(1) =4a(2) =28a(3) =244a(4) =2380a(5) =24868a(6) =272188a(7) =3080596a(8) =35758828a(9) =423373636a(10) =5092965724a(11) =62071299892a(12) =764811509644
External references
- oeis: A103211