Consider the figure made up of a row of n adjacent congruent rectangles, with diagonals of all possible rectangles drawn; a(n) is the number of interior vertices where exactly four lines cross.

A336490

Consider the figure made up of a row of n adjacent congruent rectangles, with diagonals of all possible rectangles drawn; a(n) is the number of interior vertices where exactly four lines cross.

Terms

    a(0) =0a(1) =0a(2) =1a(3) =2a(4) =2a(5) =10a(6) =22a(7) =18a(8) =32a(9) =62a(10) =100a(11) =118a(12) =136a(13) =154a(14) =274a(15) =346a(16) =426a(17) =554a(18) =698a(19) =726a(20) =884a(21) =1058a(22) =1248a(23) =1454a(24) =1784a(25) =2146a(26) =2714a(27) =2978a(28) =3250a(29) =3722

External references