Number of n X 2 0..3 arrays x(i,j) with each element horizontally or vertically next to at least one element with value (x(i,j)+1) mod 4 and at least one element with value (x(i,j)-1) mod 4, no adjacent elements equal, and upper left element zero.

A230893

Number of n X 2 0..3 arrays x(i,j) with each element horizontally or vertically next to at least one element with value (x(i,j)+1) mod 4 and at least one element with value (x(i,j)-1) mod 4, no adjacent elements equal, and upper left element zero.

Terms

    a(0) =0a(1) =2a(2) =2a(3) =10a(4) =22a(5) =70a(6) =186a(7) =538a(8) =1494a(9) =4230a(10) =11866a(11) =33434a(12) =94006a(13) =264582a(14) =744314a(15) =2094362a(16) =5892502a(17) =16579462a(18) =46647706a(19) =131248794a(20) =369281782a(21) =1039014534a(22) =2923376826a(23) =8225233690a(24) =23142568790a(25) =65114084998a(26) =183205408986a(27) =515467935386

External references