Number of (w,x,y,z) with all terms in {0,...,n} and (least gapsize)<2.

Terms

a(0) =1a(1) =16a(2) =79a(3) =240a(4) =551a(5) =1066a(6) =1839a(7) =2924a(8) =4375a(9) =6246a(10) =8591a(11) =11464a(12) =14919a(13) =19010a(14) =23791a(15) =29316a(16) =35639a(17) =42814a(18) =50895a(19) =59936a(20) =69991a(21) =81114a(22) =93359a(23) =106780a(24) =121431a(25) =137366a(26) =154639a(27) =173304a(28) =193415a(29) =215026