a(n) = Sum_{k=0..n} binomial(k+6,6) * binomial(2*k,2*n-2*k).

Terms

a(0) =1a(1) =7a(2) =35a(3) =252a(4) =1498a(5) =7602a(6) =36498a(7) =165600a(8) =713769a(9) =2957647a(10) =11850223a(11) =46111352a(12) =174956250a(13) =649284286a(14) =2362771938a(15) =8449241836a(16) =29744151416a(17) =103237104740a(18) =353744829032