Numerator sequence of mean length of certain stackings of n+1 squares on a double staircase.

Terms

a(0) =1a(1) =1a(2) =5a(3) =12a(4) =28a(5) =61a(6) =127a(7) =257a(8) =507a(9) =982a(10) =1872a(11) =3523a(12) =6557a(13) =12089a(14) =22105a(15) =40128a(16) =72380a(17) =129809a(18) =231611a(19) =411337a(20) =727455a(21) =1281578a(22) =2249856a(23) =3936935a(24) =6868537a(25) =11950033a(26) =20737613a(27) =35901300a(28) =62014396a(29) =106897669