Number of cyclic arrangements of S={1,2,...,n} such that the difference of any two neighbors is a divisor of their sum.

A242531

Number of cyclic arrangements of S={1,2,...,n} such that the difference of any two neighbors is a divisor of their sum.

Terms

    a(0) =0a(1) =1a(2) =1a(3) =1a(4) =1a(5) =4a(6) =3a(7) =9a(8) =26a(9) =82a(10) =46a(11) =397a(12) =283a(13) =1675a(14) =9938a(15) =19503a(16) =10247a(17) =97978a(18) =70478a(19) =529383a(20) =3171795a(21) =7642285a(22) =3824927a(23) =48091810a(24) =116017829a(25) =448707198a(26) =1709474581a(27) =6445720883a(28) =3009267707a(29) =51831264296

External references