a(n) = Sum_{1 <= i < j < k < m <= n} (m*k*j*i)^2.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =576a(5) =21076a(6) =296296a(7) =2475473a(8) =14739153a(9) =68943381a(10) =268880381a(11) =909450751a(12) =2742417535a(13) =7522650135a(14) =19058554515a(15) =45123156390a(16) =100771975590a(17) =213877057086a(18) =434042943246a(19) =846542846578