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!)
A090516 Perfect powers (at least a square) in which neighboring digits are distinct. 4

%I #13 Sep 03 2018 02:50:21

%S 1,4,8,9,16,25,27,32,36,49,64,81,121,125,128,169,196,216,243,256,289,

%T 324,343,361,484,512,529,576,625,676,729,784,841,961,1024,1089,1296,

%U 1369,1521,1681,1728,1764,1849,1936,2025,2048,2187,2197,2304,2401,2601

%N Perfect powers (at least a square) in which neighboring digits are distinct.

%C Sequence must be infinite but a proof is needed. Subsidiary sequences; Perfect squares or perfect cubes etc. in which neighboring digits are distinct.

%C On the other hand, for k >= 22 we might expect only finitely many k-th powers where neighboring digits are distinct (see A318763). - _Robert Israel_, Sep 03 2018

%H Robert Israel, <a href="/A090516/b090516.txt">Table of n, a(n) for n = 1..10000</a>

%p N:= 5000:

%p filter:= proc(n) local L;

%p L:= convert(n,base,10);

%p not member(0, L[2..-1]-L[1..-2])

%p end proc:

%p P:= sort(convert({seq(seq(i^k,i=1..floor(N^(1/k))),k=2..ilog2(N))},list)):

%p select(filter, P); # _Robert Israel_, Sep 03 2018

%Y Cf. A001597 (perfect powers), A075309 (distinct-digit perfect powers), A318763.

%K base,easy,nonn

%O 1,2

%A _Amarnath Murthy_, Dec 06 2003

%E Corrected and extended by _Rick L. Shepherd_, Jul 01 2005

%E Offset corrected by _Robert Israel_, Sep 03 2018

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 March 29 02:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)