Half the number of 0..n arrays of length 6 with second differences nonzero.

Terms

a(0) =13a(1) =162a(2) =1238a(3) =5104a(4) =16594a(5) =43727a(6) =101743a(7) =211461a(8) =408430a(9) =735896a(10) =1261599a(11) =2064329a(12) =3259612a(13) =4975687a(14) =7395946a(15) =10715635a(16) =15205983a(17) =21151890a(18) =28937100a(19) =38956477a(20) =51737361a(21) =67810309a(22) =87873466a(23) =112625630a(24) =142969752a(25) =179799242