OFFSET
0,4
COMMENTS
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..50
Gus Wiseman, The a(4) = 48 graphs with distinct rotations.
FORMULA
a(n > 0) = A306715(n) * n.
a(n) = Sum_{d|n} mu(d)*2^(n*(n/d-1)/2 + n*floor(d/2)/d) for n > 0. - Andrew Howroyd, Aug 15 2019
MATHEMATICA
rotgra[g_, m_]:=Sort[Sort/@(g/.k_Integer:>If[k==m, 1, k+1])];
Table[Length[Select[Subsets[Subsets[Range[n], {2}]], UnsameQ@@Table[Nest[rotgra[#, n]&, #, j], {j, n}]&]], {n, 0, 5}]
PROG
(PARI) a(n)={if(n==0, 1, sumdiv(n, d, moebius(d)*2^(n*(n/d-1)/2 + n*(d\2)/d)))} \\ Andrew Howroyd, Aug 15 2019
(Python)
from sympy import mobius, divisors
def A324461(n): return sum(mobius(m:=n//d)<<(n*(d-1)>>1)+d*(m>>1) for d in divisors(n, generator=True)) if n else 1 # Chai Wah Wu, Jul 03 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Feb 28 2019
EXTENSIONS
Terms a(7) and beyond from Andrew Howroyd, Aug 15 2019
STATUS
approved