cp's OEIS Frontend

A387070 Remove every digit that appears in n from the decimal representation of n^2. If no digits remain, set a(n) = 0.

%I A387070 #23 Aug 21 2025 09:56:29
%S A387070 0,0,4,9,16,2,3,49,64,81,0,2,44,69,96,22,25,289,324,36,4,44,484,59,
%T A387070 576,6,7,9,74,841,9,96,104,1089,1156,122,129,169,1444,1521,16,68,176,
%U A387070 189,1936,202,211,2209,230,201,2,260,704,2809,2916,302,313,3249,3364,3481,3,372,3844,99,9,422,435
%N A387070 Remove every digit that appears in n from the decimal representation of n^2. If no digits remain, set a(n) = 0.
%F A387070 a(n) = A258682(n) for n <= 19.
%F A387070 From _David A. Corneth_, Aug 16 2025: (Start)
%F A387070 a(A029793(k)) = 0.
%F A387070 a(A029783(k)) = A029783(k)^2. (End)
%e A387070 a(25) = 6 since 25^2 = 625 and once we remove the 2 and 5, we are left with 6.
%e A387070 a(26) = 7 since 26^2 = 676 and once we remove the 6, we are left with 7.
%t A387070 a[n_] := FromDigits[Select[IntegerDigits[n^2], FreeQ[IntegerDigits[n], #] &]]; Array[a, 100, 0] (* _Amiram Eldar_, Aug 16 2025 *)
%o A387070 (PARI) a(n)={my(S=Set(digits(n))); fromdigits(select(x->!setsearch(S,x), digits(n^2)))} \\ _Andrew Howroyd_, Aug 15 2025
%o A387070 (Python)
%o A387070 def A387070(k):
%o A387070     s = set(str(k))
%o A387070     t = "".join(d for d in str(k**2) if d not in s)
%o A387070     return int(t) if t != "" else 0
%o A387070 print([A387070(n) for n in range(67)]) # _Michael S. Branicky_, Aug 16 2025
%Y A387070 Cf. A029793, A258682.
%K A387070 nonn,base,new
%O A387070 0,3
%A A387070 _Ali Sada_, Aug 15 2025