%I A035497
%S A035497 7,13,19,23,31,79,97,103,109,139,167,193,239,263,293,313,331,367,379,
%T A035497 383,397,409,487,563,617,653,673,683,709,739,761,863,881,907,937,1009,
%U A035497 1033,1039,1093,1151,1277,1303,1373,1427,1447,1481,1487,1511,1607,1663
%N A035497 Happy primes: primes that eventually reach 1 under iteration of "x -> 
               sum of squares of digits of x".
%C A035497 Contribution from Thomas M. Green (tgreen(AT)astound.net), Oct 23 2009: 
               (Start)
%C A035497 The 2nd and 3rd repunit primes, 1111111111111111111 and 11111111111111111111111
%C A035497 are happy primes. (End)
%D A035497 R. K. Guy, Unsolved Problems Number Theory, Sect. E34.
%H A035497 C. Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_021.htm">
               Related puzzle page</a>
%H A035497 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               HappyNumber.html">Link to a section of The World of Mathematics.</
               a>
%H A035497 Wikipedia, <a href="http://en.wikipedia.org/wiki/Happy_number">Happy 
               number</a>
%H A035497 Doctor Who, <a href="http://www.youtube.com/watch?v=ee2If8jSxUo">Episode 
               42</a>
%H A035497 Wikipedia, <a href="http://en.wikipedia.org/wiki/42_(Doctor_Who)">Doctor 
               Who, Episode 42</a>
%Y A035497 Cf. A007770 (happy nu mbers), A046519.
%Y A035497 Sequence in context: A049591 A058620 A038910 this_sequence A059335 A070419 
               A080199
%Y A035497 Adjacent sequences: A035494 A035495 A035496 this_sequence A035498 A035499 
               A035500
%K A035497 nonn,easy,base
%O A035497 1,1
%A A035497 N. J. A. Sloane (njas(AT)research.att.com).
%E A035497 More terms from Patrick De Geest (pdg(AT)worldofnumbers.com), Oct 15 
               1999.
%E A035497 Doctor Who links from David Applegate, Oct 06 2008