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) =13a(4) =28a(5) =55a(6) =92a(7) =147a(8) =216a(9) =309a(10) =420a(11) =561a(12) =724a(13) =923a(14) =1148a(15) =1415a(16) =1712a(17) =2057a(18) =2436a(19) =2869a(20) =3340a(21) =3871a(22) =4444a(23) =5083a(24) =5768a(25) =6525a(26) =7332a(27) =8217a(28) =9156a(29) =10179