A171250 Row lengths of A082381: number of iterations of "sum of digits squared" until 1 or 4 is reached.
1, 1, 11, 1, 8, 13, 5, 9, 10, 1, 2, 9, 2, 10, 10, 7, 9, 9, 4, 1, 9, 10, 3, 2, 7, 9, 10, 3, 6, 11, 2, 3, 10, 8, 9, 12, 6, 7, 11, 8, 10, 2, 8, 4, 11, 8, 9, 10, 4, 8, 10, 7, 9, 11, 9, 8, 10, 5, 8, 13, 7, 9, 12, 8, 8, 11, 6, 2, 12, 5, 9, 10, 6, 9, 10, 6, 5, 4, 3, 9, 9, 3, 7, 10, 5, 2, 4, 14, 4, 10, 4, 6, 11, 4, 8, 12, 3, 4, 12, 1
Offset: 1
Crossrefs
Programs
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Mathematica
Table[Length[NestWhileList[Total[IntegerDigits[#]^2]&,n,!MemberQ[{1,4},#]&]]-1,{n,100}]/.(0->1) (* Harvey P. Dale, Jun 08 2017 *)
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PARI
A171250(n)=my(c=0); until( n==4 || n==1, c++; n=norml2(eval(Vec(Str(n))))); c
Formula
a(n) = O(log* n).
Extensions
Formula from Charles R Greathouse IV, Aug 02 2010
Corrected and extended by Harvey P. Dale, Jun 08 2017
Comments