Suppose e<f, e<h, g<f and g<h. To avoid fegh means not to have four consecutive letters such that the second and the third letters are less than the first and the fourth letters.
A177482
Suppose e<f, e<h, g<f and g<h. To avoid fegh means not to have four consecutive letters such that the second and the third letters are less than the first and the fourth letters.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =6a(4) =20a(5) =80a(6) =360a(7) =1888a(8) =11168a(9) =75168a(10) =560960a(11) =4632320a(12) =41627520a(13) =405993472a(14) =4256566784a(15) =47855992320a(16) =573443425280
External references
- oeis: A177482