OFFSET
1,2
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..550
MATHEMATICA
hapQ[n_]:=MemberQ[NestList[Total[IntegerDigits[#]^2]&, n, 15], 1]; Select[ LinearRecurrence[{1, 1, 1}, {1, 1, 2}, 150], hapQ] (* Harvey P. Dale, Jun 05 2011 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Levrand Roland (roland.levrand(AT)gmx.ch), Apr 09 2009
STATUS
approved