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A091837
Smallest b>1 such that 11*n is a repdigit in base b.
1
10, 10, 10, 10, 10, 10, 10, 10, 10, 21, 3, 21, 12, 13, 14, 15, 16, 17, 18, 19, 20, 3, 22, 21, 24, 21, 26, 21, 28, 21, 4, 21, 32, 21, 34, 21, 36, 21, 32, 21, 40, 32, 42, 43, 32, 45, 46, 23, 48, 24, 32, 25, 52, 26, 54, 27, 32, 28, 58, 29, 60, 4, 32, 31, 54, 32, 66, 33, 32
OFFSET
1,1
COMMENTS
a(n) <= n-1 for n >= 12. - Robert Israel, Apr 13 2021
LINKS
Eric Weisstein's World of Mathematics, Repdigit
EXAMPLE
n=11: 121=11*11 in binary = '1111001', but in ternary = '11111', therefore a(11)=3;
n=93: 1023=11*93 in binary = '1111111111', therefore a(93)=2.
MAPLE
f:= proc(n) local b, d, m;
for b from 2 do
d:= (11*n) mod b;
m:= ceil(log[b](11*n));
if 11*n = d*(b^m-1)/(b-1) then return b fi
od
end proc:
map(f, [$1..100]); # Robert Israel, Apr 13 2021
CROSSREFS
Cf. A008593.
Sequence in context: A376257 A169932 A245403 * A316650 A216875 A166710
KEYWORD
nonn,base,look
AUTHOR
Reinhard Zumkeller, Mar 10 2004
STATUS
approved