a(n) = number of permutations <p(1), p(2), ..., p(n)> of <1, 2, ..., n>, such that p(k) > p(k-1) when k is composite and p(k) < p(k-1) when k is prime.
A097277
a(n) = number of permutations <p(1), p(2), ..., p(n)> of <1, 2, ..., n>, such that p(k) > p(k-1) when k is composite and p(k) < p(k-1) when k is prime.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =3a(4) =9a(5) =35a(6) =155a(7) =791a(8) =2590a(9) =6756a(10) =59091a(11) =414986a(12) =3520583a(13) =31103150a(14) =168701533a(15) =701447397a(16) =9487636929a(17) =99912639989
External references
- oeis: A097277