OFFSET
1,8
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
EXAMPLE
29 -> 2 + 9 = 11 -> 1 + 1 = 2 -> persistence = 2
487 -> 4 + 8 + 7 = 19 -> 1 + 9 = 10 -> 1 + 0 = 1 -> persistence = 3
MAPLE
P:=proc(n) local i, k, w, ok, cont; for i from 1 by 1 to n do k:=ithprime(i); w:=0; ok:=1; if k<10 then print(0); else cont:=1; while ok=1 do while k>0 do w:=w+(k-(trunc(k/10)*10)); k:=trunc(k/10); od; if w<10 then ok:=0; print(cont); else cont:=cont+1; k:=w; w:=1; fi; od; fi; od; end: P(100);
MATHEMATICA
Table[Length[NestWhileList[Total[IntegerDigits[#]]&, n, #>9&]]-1, {n, Prime[ Range[100]]}] (* Harvey P. Dale, Aug 05 2014 *)
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Paolo P. Lava and Giorgio Balzarotti, Jun 22 2007
STATUS
approved