OFFSET
1,2
COMMENTS
A meander is a closed curve drawn by arcs of equal length and central angles of equal magnitude, starting with a positively oriented arc.
a(n) = 2^(n-1) + 1 iff n is prime.
LINKS
Peter Luschny, Meander.
FORMULA
a(n) = Sum_{d|n} A198060(d-1,n/d-1).
MAPLE
MATHEMATICA
A198060[m_, n_] := Sum[ Sum[ Sum[(-1)^(j+i)*Binomial[i, j]* Binomial[n, k]^(m+1)*(n+1)^j*(k+1)^(m-j)/(k+1)^m, {i, 0, m}], {j, 0, m}], {k, 0, n}]; a[n_] := Sum[ A198060[d-1, n/d-1], {d, Divisors[n]}]; Table[a[n], {n, 1, 34}] (* Jean-François Alcover, Jun 27 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Nov 20 2011
STATUS
approved