A094406 - OEIS

A094406

Smallest unhappy number that takes n steps to reach any of the unhappy cycle (4, 16, 37, 58, 89, 145, 42, 20) under iteration of sum of squares of digits map.

%I #7 Jul 11 2015 01:00:34

%S 4,2,11,15,5,3,14,45,36,6,112,269,15999

%N Smallest unhappy number that takes n steps to reach any of the unhappy cycle (4, 16, 37, 58, 89, 145, 42, 20) under iteration of sum of squares of digits map.

%C This sequence is an analog of sequence A001273 with the unhappy numbers instead of the happy numbers.

%H W. Schneider, <a href="http://web.archive.org/web/2004/www.wschnei.de/digit-related-numbers/happy-numbers.html">Unhappy Numbers</a>.

%e 15 is the fourth term because: 15: 1^2 + 5^2 = 26 / 26: 2^2 + 6^2 = 40 / 40: 4^2 + 0^2 = 16 and 16 is a member of the unhappy number series (4, 16, 37, 58, 89, 145, 42, 20)

%Y Cf. A001273.

%K nonn,base

%O 4,1

%A _Sergio Pimentel_, Apr 30 2004

%E The next term, 577999999999....999999999999 (199 digits) is too large to include.

%E Edited by _Charles R Greathouse IV_, Aug 03 2010