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A104166
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Repdigit Smith numbers.
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2
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4, 22, 666, 1111, 6666666, 4444444444, 44444444444444444444, 555555555555555555555555555, 55555555555555555555555555555555, 4444444444444444444444444444444444444444444444444444444
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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d[n_]:=IntegerDigits[n]; tr[n_]:=Transpose[FactorInteger[n]]; a[n_]:=NestList[FromDigits[Flatten[d[{#, n}]]]&, n, 55]; t={}; Do[If[!PrimeQ[n]&&Total[d[n]]==Total[d@tr[n][[1]]*tr[n][[2]], 2], AppendTo[t, n]], {n, Drop[Union[Flatten[Table[a[k], {k, 9}]]], 1]}]; t (* Jayanta Basu, Jun 04 2013 *)
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PROG
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(Python)
from sympy import factorint
from itertools import product
def sd(n): return sum(map(int, str(n)))
def smith(n):
f = factorint(n)
return sum(f[p] for p in f) > 1 and sd(n) == sum(sd(p)*f[p] for p in f)
def repsto(limit):
yield from range(min(limit, 9)+1)
for rep in range(2, 10**len(str(limit))):
for digit in "123456789":
out = int(digit*rep)
if out > limit: return
yield out
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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