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A083278 Repunit powers. 7
1, 11, 111, 121, 1111, 1331, 11111, 12321, 14641, 111111, 161051, 1111111, 1234321, 1367631, 1771561, 11111111, 19487171, 111111111, 123454321, 151807041, 214358881, 1111111111, 1371330631, 2357947691, 11111111111 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Eric Weisstein's World of Mathematics, Repunit

Wikipedia, Repunit

EXAMPLE

a(13)=1234321=1111^2; a(14)=1367631=111^3; a(15)=1771561=11^6.

MATHEMATICA

With[{intlen=12}, Select[Union[Flatten[#^Range[intlen]&/@(FromDigits/@ Table[ PadRight[{}, n, 1], {n, intlen}])]], IntegerLength[#]<=intlen&]] (* Harvey P. Dale, Apr 25 2016 *)

PROG

(Haskell)

import Data.Set (empty, findMin, deleteMin, deleteMin, insert)

import qualified Data.Set as Set (null)

a083278 n = a083278_list !! (n-1)

a083278_list = 1 : f empty (drop 2 a002275_list) where

   f rups rus'@(ru:rus)

     | Set.null rups || m > ru = f (insert (ru, ru) rups) rus

     | otherwise = m : f (insert (m*m', m') (deleteMin rups)) rus'

     where (m, m') = findMin rups

-- Reinhard Zumkeller, Feb 05 2012

(PARI) lista(nn) = {my(list = List(), r); for (n=1, nn, my(r = (10^n-1)/9); listput(list, r); if (r > 1, my(e=2); while(#Str(x=r^e) <= nn, listput(list, x); e++)); ); Vec(vecsort(list)); } \\ Michel Marcus, May 28 2019

CROSSREFS

Cf. A002275, A206245.

Sequence in context: A135464 A231872 A308365 * A039987 A039989 A039990

Adjacent sequences:  A083275 A083276 A083277 * A083279 A083280 A083281

KEYWORD

nonn,base

AUTHOR

Reinhard Zumkeller, Jun 02 2003

STATUS

approved

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Last modified April 17 23:03 EDT 2021. Contains 343071 sequences. (Running on oeis4.)