login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A048330 Numbers that are repdigits in base 5. 4
0, 1, 2, 3, 4, 6, 12, 18, 24, 31, 62, 93, 124, 156, 312, 468, 624, 781, 1562, 2343, 3124, 3906, 7812, 11718, 15624, 19531, 39062, 58593, 78124, 97656, 195312, 292968, 390624, 488281, 976562, 1464843, 1953124, 2441406, 4882812, 7324218, 9765624 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..400

Eric Weisstein's World of Mathematics, Repdigit.

FORMULA

Conjecture: G.f.: x*(1+2*x+3*x^2+4*x^3) / ( (x-1)*(1+x)*(x^2+1)*(5*x^4-1) ) with a(n) = 6*a(n-4) - 5*a(n-8). - R. J. Mathar, Mar 15 2015

Sum_{n>=1} 1/a(n) = (25/3) * A248722 = 2.51444877998310381623... - Amiram Eldar, Jan 21 2022

EXAMPLE

12_10 = 22_5, 18_10 = 33_5, 7812_10 = 222222_5.

MATHEMATICA

Union[Flatten[Table[FromDigits[PadRight[{}, n, d], 5], {n, 0, 40}, {d, 4}]]] (* Vincenzo Librandi, Feb 06 2014 *)

PROG

(Magma) [0] cat [k:k in [1..10^7]| #Set(Intseq(k, 5)) eq 1]; // Marius A. Burtea, Oct 11 2019

CROSSREFS

Cf. A010785, A033018, A028987, A028988, A248722.

Sequence in context: A140494 A048316 A037393 * A118651 A206292 A129297

Adjacent sequences:  A048327 A048328 A048329 * A048331 A048332 A048333

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Feb 15 1999

EXTENSIONS

Offset changed from 1 to 0 by Vincenzo Librandi, Feb 06 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 13 18:03 EDT 2022. Contains 356107 sequences. (Running on oeis4.)