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A061280 Smallest base b >= 2 for which b^n contains n as a substring. 3
10, 5, 7, 7, 5, 2, 3, 7, 3, 2, 11, 7, 6, 25, 7, 11, 4, 8, 5, 7, 6, 6, 6, 3, 4, 9, 17, 3, 6, 13, 8, 5, 8, 5, 2, 2, 2, 8, 6, 6, 5, 4, 7, 2, 6, 9, 8, 6, 2, 4, 2, 8, 6, 5, 5, 5, 3, 8, 4, 2, 3, 3, 6, 5, 6, 12, 2, 6, 3, 5, 3, 2, 2, 6, 5, 6, 3, 3, 4, 3, 4, 2, 3, 4, 2, 4, 3, 7, 2, 8, 8, 4, 2, 6, 3, 4, 7, 6, 7, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
a(3) = 7 since 7^1 contains no 1, 7^2 contains no 2 and 7^3 contains a 3.
MAPLE
a:= proc(n) local b; for b from 2 while
searchtext(""||n, ""||(b^n))=0 do od; b
end:
seq(a(n), n=1..100); # Alois P. Heinz, Sep 28 2016
MATHEMATICA
Table[b = 2; While[Length@ SequencePosition[IntegerDigits[b^n], IntegerDigits[n]] == 0, b++]; b, {n, 120}] (* Michael De Vlieger, Sep 28 2016, Version 10.1 *)
PROG
(Python)
def a(n):
b, s = 2, str(n)
while s not in str(b**n): b += 1
return b
print([a(n) for n in range(1, 101)]) # Michael S. Branicky, Oct 05 2021
CROSSREFS
Sequence in context: A097327 A226583 A007272 * A030071 A147653 A152611
KEYWORD
base,easy,look,nonn
AUTHOR
Erich Friedman, Jun 06 2001
STATUS
approved

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Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)