Number of sets of 4 distinct collinear points in an n X n permutation array in which leftmost pair has same spacing as rightmost pair.

A234471

Number of sets of 4 distinct collinear points in an n X n permutation array in which leftmost pair has same spacing as rightmost pair.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =2a(4) =10a(5) =30a(6) =86a(7) =180a(8) =344a(9) =624a(10) =1056a(11) =1626a(12) =2522a(13) =3646a(14) =5118a(15) =7164a(16) =9784a(17) =12868a(18) =16848a(19) =21438a(20) =27202a(21) =34298a(22) =42550a(23) =51800a(24) =63184a(25) =76256a(26) =91032a(27) =108086a(28) =127850a(29) =149442

External references