A052081 - OEIS

%I #17 Nov 08 2023 14:27:42

%S 0,1,2,3,4,5,6,7,8,9,10,12,13,14,15,16,17,18,19,20,21,23,24,25,27,28,

%T 29,30,31,32,33,34,35,36,37,38,40,42,43,44,46,47,48,49,50,51,52,53,54,

%U 55,57,58,59,60,61,62,64,65,66,67,69,70,71,72,73,74,76,78,79,80,82,83

%N Numbers k such that k^2 is a square whose decimal expansion's digits are grouped together.

%H Robert Israel, <a href="/A052081/b052081.txt">Table of n, a(n) for n = 1..10000</a>

%e 81 is not a term since in 81^2 = 6561, the two 6's are separated by the 5.

%e 88 is a term since in 88^2 = 7744, the 7 and 4 are grouped.

%p filter:= proc(n) local L,i,v,V;

%p   L:= convert(n^2,base,10);

%p   for i from 1 to nops(L) do

%p     v:= L[i];

%p     if not assigned(V[v]) then V[v]:= i

%p     elif V[v] < i-1 then return false

%p     else V[v]:= i

%p     fi

%p   od;

%p   true

%p end proc:

%p select(filter, [$0..100]); # _Robert Israel_, Nov 08 2023

%Y Cf. A052082, A052085, A052086, A052083, A052084.

%K nonn,base

%O 1,3

%A _Patrick De Geest_, Jan 15 2000