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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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Last modified June 28 08:24 EDT 2017. Contains 288813 sequences.