a^2+na=221 , {a^2 +2[[(a-1)/2]2-1]-[(a-2)2+2[[(a-2-1)/2]^2-1]]-34}/6=k , {(k+1)^2 +2[[((k+1)-1)/2]2-1]-[((k+1)-2)2+2*[[((k+1)-2-1)/2]^2-1]]-34}/6=0
