Number of permutations of 1..n with i-10<=p(i)<=i+2.

Terms

a(0) =1a(1) =2a(2) =6a(3) =18a(4) =54a(5) =162a(6) =486a(7) =1458a(8) =4374a(9) =13122a(10) =39366a(11) =117074a(12) =348151a(13) =1038313a(14) =3098572a(15) =9246640a(16) =27592792a(17) =82337392a(18) =245690824a(19) =733114816a(20) =2187497080a(21) =6527051536a(22) =19475245096a(23) =58109645152a(24) =173387205336a(25) =517354196145