a(n) = K_4(n) = Sum_{k>=0} A090285(4,k)*2^k*binomial(n,k). a(n) = 2*(n^4+14*n^3+62*n^2+91*n+21)/3.

Terms

a(0) =14a(1) =126a(2) =386a(3) =874a(4) =1686a(5) =2934a(6) =4746a(7) =7266a(8) =10654a(9) =15086a(10) =20754a(11) =27866a(12) =36646a(13) =47334a(14) =60186a(15) =75474a(16) =93486a(17) =114526a(18) =138914a(19) =166986a(20) =199094a(21) =235606a(22) =276906a(23) =323394a(24) =375486a(25) =433614a(26) =498226a(27) =569786a(28) =648774a(29) =735686