a(n) = n+binomial(2*n-6,n-3)+binomial(2*n-5,n-3)+binomial(n-1,n-3)+Sum_{i=1..n-3} (binomial(n+i-3,n-3)+2*n-i-5).

A274295

a(n) = n+binomial(2*n-6,n-3)+binomial(2*n-5,n-3)+binomial(n-1,n-3)+Sum_{i=1..n-3} (binomial(n+i-3,n-3)+2*n-i-5).

Terms

    a(0) =1a(1) =1a(2) =3a(3) =6a(4) =16a(5) =43a(6) =120a(7) =369a(8) =1244a(9) =4449a(10) =16424a(11) =61645a(12) =233568a(13) =890421a(14) =3409866a(15) =13105083a(16) =50517580a(17) =195234557a(18) =756198408a(19) =2934687173a(20) =11408742152a(21) =44420399805a(22) =173191793402a(23) =676104404123

External references