cp's OEIS Frontend

A031997 Odd numbers which when cubed give number composed just of the digits 0, 1, 2, 3.

%I A031997 #23 Apr 27 2025 12:32:25
%S A031997 1,11,101,1001,10001,100001,684917,1000001,10000001,100000001,
%T A031997 1000000001,10000000001,100000000001,1000000000001,10000000000001,
%U A031997 100000000000001,1000000000000001,10000000000000001,100000000000000001,1000000000000000001
%N A031997 Odd numbers which when cubed give number composed just of the digits 0, 1, 2, 3.
%C A031997 Note that 684917 (whose cube is 321302302131323213) so far is the only entry not of the form 10^x + 1.
%t A031997 Do[ If[ Union[ IntegerDigits[ n^3 ] ] [ [ -1 ] ] < 4, Print[ n ] ], {n, 1, 10^9, 2} ] (* corrected by _Friedjof Tellkamp_, Apr 24 2025 *)
%t A031997 (* faster code *)
%t A031997 DigitsLEQ3[n_] := And @@ (LessEqual[#, 3] & /@ IntegerDigits[n])
%t A031997 Arr = {1, 7}; For[i = 1, i < 10, i++, Arr = Flatten[Table[Select[Arr + 10^i j, DigitsLEQ3[Mod[#^3, 10^(i+1)]] &], {j, 0, 9}]]];
%t A031997 Select[Arr, DigitsLEQ3[#^3] &] (* _Friedjof Tellkamp_, Apr 25 2025 *)
%o A031997 (Python)
%o A031997 A031997_list = [n for n in range(1,10**6,2) if max(str(n**3)) <= '3'] # _Chai Wah Wu_, Feb 23 2016
%Y A031997 Cf. A030175, A043681, A278936, A278937.
%K A031997 nonn,base,more
%O A031997 1,2
%A A031997 _Robert G. Wilson v_, Jun 23 2001
%E A031997 Term 0 removed and a(12)-a(17) added by _Chai Wah Wu_, Feb 25 2016
%E A031997 a(18)-a(20) from _Giovanni Resta_, Mar 14 2020