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A088323 Number of numbers b>1 such that n is a repunit in base b representation. 5
0, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,6
COMMENTS
is a(n) < 4 ?;
n>2: a(n) > 0 as n = (n-1)^1 + (n-1)^0.
a(A119598(n)) > 3; a(A053696(n)) > 2; a(A085104(n)) > 2. - Reinhard Zumkeller, Jan 22 2014
LINKS
Eric Weisstein's World of Mathematics, Repunit
EXAMPLE
a(31)=3: 31 = 2^4+2^3+2^2+2^1+2^0 = 5^2+5^1+5^0 = 30^1+30^0.
PROG
(Haskell)
a088323 n = sum $ map (f n) [2 .. n-1] where
f x b = if x == 0 then 1 else if d /= 1 then 0 else f x' b
where (x', d) = divMod x b
-- Reinhard Zumkeller, Jan 22 2014
CROSSREFS
Sequence in context: A058060 A338160 A336137 * A003652 A071625 A331592
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, Nov 06 2003
EXTENSIONS
Example corrected by Reinhard Zumkeller, Jan 22 2014
STATUS
approved

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)