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A088323 Number of numbers b>1 such that n is a repunit in base b representation. 4
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

Reinhard Zumkeller, Table of n, a(n) for n = 2..10000

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

Cf. A000225, A003462, A002275, A068953.

Sequence in context: A294883 A088530 A058060 * A003652 A071625 A331592

Adjacent sequences:  A088320 A088321 A088322 * A088324 A088325 A088326

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 30 16:16 EDT 2020. Contains 333127 sequences. (Running on oeis4.)