Number of (w,x,y,z) with all terms in {1,...,n} and w<=2x and y<=3z.

Terms

a(0) =0a(1) =1a(2) =16a(3) =72a(4) =210a(5) =483a(6) =990a(7) =1760a(8) =2964a(9) =4680a(10) =7040a(11) =10176a(12) =14364a(13) =19551a(14) =26180a(15) =34320a(16) =44200a(17) =56025a(18) =70308a(19) =86800a(20) =106330a(21) =128898a(22) =154836a(23) =184416a(24) =218448a(25) =256373a(26) =299520a(27) =347760a(28) =401534a(29) =461175