cp's OEIS Frontend

A274054 Number of modified skew Dyck paths of semilength n such that the area between the x-axis and the path is n*(n+1)/2.

%I A274054 #33 Jun 19 2016 16:29:42
%S A274054 1,1,0,1,3,6,14,40,140,422,1346,4487,15234,52632,183913,651948,
%T A274054 2336751,8438406,30712379,112603500,415459873,1541646225,5750112809,
%U A274054 21548036621,81096740799,306404247854,1161863199131,4420429256826,16869986745367,64567073382731
%N A274054 Number of modified skew Dyck paths of semilength n such that the area between the x-axis and the path is n*(n+1)/2.
%C A274054 A modified skew Dyck path is a path in the first quadrant which begins at the origin, ends on the x-axis, consists of steps U=(1,1) (up), D=(1,-1) (down) and A=(-1,1) (anti-down) so that A and D steps do not overlap.
%F A274054 a(n) = A274372(n,n*(n+1)/2) = A274372(n,A000217(n)).
%e A274054 a(1) = 1:   /\
%e A274054 .
%e A274054             /\
%e A274054             \ \
%e A274054 a(3) = 1:   /  \
%e A274054 .
%e A274054                 /\                          /\
%e A274054                /  \         /\/\/\         /  \
%e A274054 a(4) = 3:   /\/    \   ,   /      \   ,   /    \/\   .
%Y A274054 Cf. A000217, A230823, A274372.
%K A274054 nonn
%O A274054 0,5
%A A274054 _Alois P. Heinz_, Jun 19 2016