G.f.: Product_{j>=1} 1/(1-x^j)^binomial(j+3,3).

Terms

a(0) =1a(1) =4a(2) =20a(3) =80a(4) =305a(5) =1072a(6) =3622a(7) =11676a(8) =36450a(9) =110240a(10) =324936a(11) =935076a(12) =2635338a(13) =7285560a(14) =19795370a(15) =52930360a(16) =139462956a(17) =362471020a(18) =930186694a(19) =2358867240a(20) =5915606398a(21) =14680528648a(22) =36073675792a(23) =87816701332a(24) =211891552280a(25) =506981067168