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A051248
n^a(n) is the smallest power of n (with a(n) > 1) which starts with n.
10
2, 8, 18, 6, 24, 10, 20, 11, 22, 2, 26, 14, 10, 8, 92, 6, 166, 5, 19, 11, 60, 39, 48, 51, 94, 42, 467, 86, 14, 66, 58, 3, 5268, 33, 58, 10, 45, 70, 23, 6, 205, 70, 31, 15, 50, 84, 248, 70, 72, 94, 107, 170, 30, 10139, 182, 136, 87, 318, 49, 10, 178, 237, 295, 99, 17, 206
OFFSET
1,1
COMMENTS
A070327(n) = n^a(n) for n > 1. - Reinhard Zumkeller, Sep 29 2011
The largest of the first 10000 terms is a(1955) = 119589011. - Giovanni Resta, May 27 2016
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..10000 (first 275 terms from Reinhard Zumkeller)
EXAMPLE
2^8 = 256 begins with 2, and 2^k does not begin with 2 for any smaller integer k > 1, so a(2) = 8.
MATHEMATICA
f[n_]:=Module[{i=2}, While[Take[IntegerDigits[n^i], IntegerLength[n]] != IntegerDigits[n], i++]; i]; Array[f, 70] (* Harvey P. Dale, Oct 04 2011 *)
PROG
(Haskell)
import Data.List (isPrefixOf)
a051248 n = 2 + length
(takeWhile (not . (show n `isPrefixOf`) . show) $ iterate (* n) (n^2))
-- Reinhard Zumkeller, Sep 29 2011
CROSSREFS
Sequence in context: A154349 A268068 A073601 * A228615 A267823 A063664
KEYWORD
nonn,base,nice
EXTENSIONS
More terms from Jud McCranie
STATUS
approved