OFFSET
2,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 2..200
Eric Weisstein's World of Mathematics, Johnson Graph
Eric Weisstein's World of Mathematics, Minimum Dominating Set
Eric Weisstein's World of Mathematics, Triangular Graph
FORMULA
a(n) = n!! for n odd.
a(n) = (n-1)!!*(1 + n*(n/2 - 1)) for n even. - Andrew Howroyd, Sep 08 2019
PROG
(PARI) a(n)={my(m=(n+1)\2); ((2*m)!/(m!*2^m))*if(n%2, 1, 1 + n*(n/2-1))} \\ Andrew Howroyd, Sep 08 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Jan 16 2019
EXTENSIONS
Terms a(14) and beyond from Andrew Howroyd, Sep 08 2019
STATUS
approved