OFFSET
0,2
COMMENTS
Part of the Newton integer square-root finding process. Establishes the upper bound a(n) >= A000196(n) for all n >= 0.
FORMULA
a(n)=b(n,1) where b(0,m)=m; b(n,m)=b(floor(n/4),m*2).
a(n)=2^ceiling(A029837(n+1)/2).
PROG
(Common Lisp)
(defun A217871 (n)
(labels ((rec (n guess)
(if (zerop n)
guess
(rec (floor n 4) (* guess 2)))))
(rec n 1))) ; James Spahlinger, Oct 14 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
James Spahlinger, Oct 13 2012
STATUS
approved