Hello, Can we find the dead link from peter Tittmann : https://www.staff.hs-mittweida.de/~peter/research/enumeration.html shown on https://oeis.org/A222200 ? thanks -- ROBERT FERRÉOL 6, Rue des Annelets 75019 PARIS 01 42 41 91 98 http://mapage.noos.fr/r.ferreol https://www.facebook.com/mathcurve maths, ex mpsi Fénelon Paris