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A094830
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Start with n, repeatedly replace x by x + sum of squares of digits of x until you reach a prime; sequence gives number of steps.
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3
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1, 0, 0, 6, 0, 4, 0, 11, 5, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 5, 13, 9, 0, 4, 11, 12, 17, 3, 0, 8, 0, 8, 7, 1, 7, 3, 0, 5, 7, 4, 0, 3, 0, 3, 7, 8, 0, 2, 2, 2, 6, 3, 0, 10, 2, 3, 1, 3, 0, 3, 0, 2, 2, 18, 2, 11, 0, 2, 6, 9, 0, 10, 0, 1, 1, 2, 5, 1, 0, 16, 2, 8, 0, 3, 11, 6, 10, 2, 0, 4, 1, 15, 2, 1, 9, 2, 0, 7, 7, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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EXAMPLE
| a(4)=6 because 4 -> 20 -> 24 -> 44 -> 76 -> 161 -> 199, takes 6 steps to reach a prime.
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MATHEMATICA
| p[n_]:=Length[NestWhileList[#+Total[IntegerDigits[#]^2]&, n, !PrimeQ[ #]&]]-1; Array[p, 100] (* From Harvey P. Dale, Dec 03 2011 *)
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CROSSREFS
| Cf. A003132.
Sequence in context: A089841 A202542 A019766 * A196878 A021947 A073010
Adjacent sequences: A094827 A094828 A094829 * A094831 A094832 A094833
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KEYWORD
| base,easy,nonn
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AUTHOR
| Jason Earls (zevi_35711(AT)yahoo.com), Jun 13 2004
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