cp's OEIS Frontend

A023061 Positive numbers k such that k and 2*k are anagrams in base 5 (written in base 5).

%I A023061 #18 Aug 07 2025 03:01:09
%S A023061 13,130,143,1300,1313,1430,1443,13000,13013,13130,13143,14300,14313,
%T A023061 14430,14443,102342,103242,120234,120324,130000,130013,130130,130143,
%U A023061 131300,131313,131430,131443,143000,143013,143130,143143,144300,144313
%N A023061 Positive numbers k such that k and 2*k are anagrams in base 5 (written in base 5).
%C A023061 From _Robert Israel_, Aug 08 2018: (Start)
%C A023061 The concatenation of two terms is a term.
%C A023061 If a*10^m + b is a term, where b < (2/9)*10^m, then a*10^k+b is a term for all k > m. (End)
%H A023061 Amiram Eldar, <a href="/A023061/b023061.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..2000 from Robert Israel)
%p A023061 f:= proc(n) local L, M;
%p A023061    L:= convert(n, base, 5);
%p A023061    M:= convert(2*n, base, 5);
%p A023061    if sort(L) = sort(M) then add(L[i]*10^(i-1), i=1..nops(L)) else NULL fi
%p A023061 end proc:
%p A023061 map(f, [$1..10000]); # _Robert Israel_, Aug 08 2018
%t A023061 FromDigits[IntegerDigits[#, 5]] & /@ Select[Range[10000], SameQ @@ Sort /@ IntegerDigits[{#, 2*#}, 5] &] (* _Amiram Eldar_, Aug 06 2025 *)
%Y A023061 Cf. A007091.
%K A023061 nonn,base
%O A023061 1,1
%A A023061 _David W. Wilson_