A083278 Repunit powers.

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

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