Convolution of A001950 with itself.

Terms

a(0) =4a(1) =20a(2) =53a(3) =110a(4) =201a(5) =330a(6) =504a(7) =730a(8) =1013a(9) =1364a(10) =1787a(11) =2288a(12) =2880a(13) =3564a(14) =4348a(15) =5240a(16) =6243a(17) =7370a(18) =8624a(19) =10010a(20) =11540a(21) =13214a(22) =15045a(23) =17038a(24) =19196a(25) =21536a(26) =24056a(27) =26764a(28) =29671a(29) =32776