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 A090425 Number of iterations required for happy number A007770(n) to converge to 1. 2
 1, 6, 2, 3, 5, 4, 4, 3, 4, 5, 5, 3, 6, 4, 4, 3, 5, 5, 4, 2, 3, 5, 4, 3, 6, 6, 4, 4, 5, 5, 4, 6, 4, 4, 4, 6, 4, 6, 6, 6, 6, 4, 4, 6, 3, 4, 3, 6, 6, 4, 6, 6, 6, 5, 7, 6, 7, 6, 6, 6, 7, 5, 6, 6, 6, 7, 5, 5, 5, 4, 4, 7, 5, 5, 5, 7, 7, 4, 7, 4, 5, 3, 4, 6, 6, 6, 7, 6, 6, 4, 7, 7, 4, 5, 5, 4, 6, 3, 6, 7, 6, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The count includes both the start and end. LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Happy Number T. Cai, Xia Zhou, On the heights of happy numbers, Rocky Mount. J. Math. 38 (6) (2008) 1921. [From R. J. Mathar, Apr 22 2010] EXAMPLE 7 is the 2nd happy number and iterated digit squarings and additions give the sequence {7,49,97,130,10,1}, so a(2)=6. PROG (Haskell) a090425 n = snd \$ until ((== 1) . fst)                         (\(u, v) -> (a003132 u, v + 1)) (a007770 n, 1) -- Reinhard Zumkeller, Aug 07 2012 CROSSREFS Cf. A007770. Cf. A003132. Sequence in context: A134105 A167509 A011362 * A160081 A240937 A178054 Adjacent sequences:  A090422 A090423 A090424 * A090426 A090427 A090428 KEYWORD nonn,base AUTHOR Eric W. Weisstein, Nov 30 2003 STATUS approved

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