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

Terms

a(0) =0a(1) =1a(2) =4a(3) =17a(4) =46a(5) =89a(6) =154a(7) =251a(8) =374a(9) =531a(10) =736a(11) =979a(12) =1268a(13) =1621a(14) =2024a(15) =2485a(16) =3026a(17) =3629a(18) =4302a(19) =5071a(20) =5914a(21) =6839a(22) =7876a(23) =8999a(24) =10216a(25) =11561a(26) =13004a(27) =14553a(28) =16246a(29) =18049