A067307 One-fourth of fourth column of triangle A067304.

7, 71, 768, 8920, 109232, 1390800, 18237952, 244701440, 3343713024, 46374830848, 651170275328, 9238908291072, 132251092529152, 1907671386263552, 27701755840561152, 404632598092447744

Offset: 0

Author

Wolfdieter Lang, Feb 05 2002

Keywords

• nonn
• easy

Formula

a(n)= A067304(n+3, 3)/4 = (A067297(n+3)-(b(n+3)+b(n+2)+4*b(n+1)))/4, n>=0, with b(n) := A064340(n).

G.f.: 4(3+10*c(4*x)+12*c(4*x)^2+3*c(4*x)^3)*(c(4*x)^3)/(1+c(4*x))^4, with c(x) g.f. of A000108 (Catalan).