1,2

Example 3480 belongs to the sequence, because 34^2-80 = 1076 --> 10^2-76 = 24 --> 2^2-4 = 0

Nice zoomable picture of the directed graph (up to 1000) :

http://vargo.chez.com/upto1000.jpg

or if you prefer a GIF :

http://vargo.chez.com/upto1000.gif

The terms up to 11000 :

http://vargo.chez.com/upto11000.txt

Table of n, a(n) for n=1..20.

Sequence in context: A213991 A269100 A213062 * A061043 A098603 A274620

Adjacent sequences: A157753 A157754 A157755 * A157757 A157758 A157759

base,easy,nonn

Jean-Marc Falcoz, Mar 06 2009

approved