3,2

Increasing modular 3-sequences are of the following form: i,i+1,i+2, where arithmetic is modulo n, while correspondingly decreasing modular 3-sequences are of the form i,i-1,i-2, where arithmetic is modulo n.

Let b(n) be the sequence A165964. Then this sequence a(n)=n(b(n)).

For n=4 there are a(4)=16 solutions, thus there are 4!-a(4)=8 permutations of length 4 with increasing or decreasing modular 3-sequences. These are the permutations (0,1,2,3), (0,3,2,1), (1,2,3,0), (1,0,3,2), (2,3,0,1), (2,1,0,3), (3,0,1,2), and (3,2,1,0).

Cf. A095816, A165964, A078628.

Sequence in context: A050468 A068778 A034570 this_sequence A069840 A000817 A119508

Adjacent sequences: A165960 A165961 A165962 this_sequence A165964 A165965 A165966

nonn

Isaac E. Lambert (lamberti09(AT)mail.wlu.edu), Oct 07 2009