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

Terms

a(0) =0a(1) =1a(2) =2a(3) =7a(4) =16a(5) =33a(6) =52a(7) =87a(8) =126a(9) =181a(10) =246a(11) =331a(12) =422a(13) =545a(14) =674a(15) =831a(16) =1006a(17) =1213a(18) =1428a(19) =1691a(20) =1964a(21) =2277a(22) =2614a(23) =2995a(24) =3388a(25) =3845a(26) =4314a(27) =4835a(28) =5388a(29) =5997