4-fold convolution of A001700(n), n >= 0.

Terms

a(0) =1a(1) =12a(2) =94a(3) =608a(4) =3525a(5) =19044a(6) =97954a(7) =486000a(8) =2345930a(9) =11081880a(10) =51447036a(11) =235454848a(12) =1064832173a(13) =4767347796a(14) =21160397050a(15) =93223960784a(16) =408037319262