a(n) = n * Sum_{d|n} binomial(d+3,4)/d.

Terms

a(0) =1a(1) =7a(2) =18a(3) =49a(4) =75a(5) =177a(6) =217a(7) =428a(8) =549a(9) =890a(10) =1012a(11) =1824a(12) =1833a(13) =2849a(14) =3360a(15) =4732a(16) =4862a(17) =7506a(18) =7334a(19) =10810a(20) =11382a(21) =14729a(22) =14973a(23) =22188a(24) =20850a(25) =27482a(26) =29052a(27) =37408a(28) =35989a(29) =50490