Number of different ways to select 4 disjoint subsets from {1..n} with equal element sum.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =1a(7) =3a(8) =9a(9) =23a(10) =67a(11) =203a(12) =693a(13) =2584a(14) =9929a(15) =37480a(16) =137067a(17) =522854a(18) =2052657a(19) =8199728a(20) =33456333a(21) =137831268a(22) =574295984a(23) =2392149818a(24) =9950364020a(25) =41860671346a(26) =177512155194a(27) =757447761138