Number of permutations of length n in the 2x2 double-chevron permutation grid class.

A163824

Number of permutations of length n in the 2x2 double-chevron permutation grid class.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =106a(6) =470a(7) =2038a(8) =8624a(9) =35754a(10) =145902a(11) =588358a(12) =2351910a(13) =9341814a(14) =36936146a(15) =145567966a(16) =572415344a(17) =2247578314a(18) =8816986046a(19) =34570684966a(20) =135522530174a(21) =531285354214

External references