cp's OEIS Frontend

A052081 Numbers k such that k^2 is a square whose decimal expansion's digits are grouped together.

%I A052081 #17 Nov 08 2023 14:27:42
%S A052081 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 A052081 29,30,31,32,33,34,35,36,37,38,40,42,43,44,46,47,48,49,50,51,52,53,54,
%U A052081 55,57,58,59,60,61,62,64,65,66,67,69,70,71,72,73,74,76,78,79,80,82,83
%N A052081 Numbers k such that k^2 is a square whose decimal expansion's digits are grouped together.
%H A052081 Robert Israel, <a href="/A052081/b052081.txt">Table of n, a(n) for n = 1..10000</a>
%e A052081 81 is not a term since in 81^2 = 6561, the two 6's are separated by the 5.
%e A052081 88 is a term since in 88^2 = 7744, the 7 and 4 are grouped.
%p A052081 filter:= proc(n) local L,i,v,V;
%p A052081   L:= convert(n^2,base,10);
%p A052081   for i from 1 to nops(L) do
%p A052081     v:= L[i];
%p A052081     if not assigned(V[v]) then V[v]:= i
%p A052081     elif V[v] < i-1 then return false
%p A052081     else V[v]:= i
%p A052081     fi
%p A052081   od;
%p A052081   true
%p A052081 end proc:
%p A052081 select(filter, [$0..100]); # _Robert Israel_, Nov 08 2023
%Y A052081 Cf. A052082, A052085, A052086, A052083, A052084.
%K A052081 nonn,base
%O A052081 1,3
%A A052081 _Patrick De Geest_, Jan 15 2000