cp's OEIS Frontend

A258682 Remove from n^2 all digits of n from left to right, in decimal representation.

%I A258682 #10 Jun 11 2015 10:14:05
%S A258682 0,0,4,9,16,2,3,49,64,81,0,2,44,69,96,22,25,289,324,36,40,44,484,59,
%T A258682 576,6,76,9,74,841,90,96,104,1089,1156,122,129,169,1444,1521,160,681,
%U A258682 176,189,1936,202,211,2209,230,201,20,260,704,2809,2916,302,313
%N A258682 Remove from n^2 all digits of n from left to right, in decimal representation.
%C A258682 a(A029783(n)) = A029783(n)^2; a(A189056(n)) < A189056(n)^2;
%C A258682 a(A178501(n)) = 0.
%H A258682 Reinhard Zumkeller, <a href="/A258682/b258682.txt">Table of n, a(n) for n = 0..10000</a>
%e A258682 .    n   n^2 |  a(n)
%e A258682 . -----------+------
%e A258682 .   20   400 |    40
%e A258682 .   21   441 |    44
%e A258682 .   22   484 |   484
%e A258682 .   23   529 |    59
%e A258682 .   24   576 |   576
%e A258682 .   25   625 |     6
%e A258682 .   26   676 |    76  not 67, as digits of n are to be removed
%e A258682 .   27   729 |     9                                  from left to right
%e A258682 .   28   784 |    74
%e A258682 .   29   841 |   841
%e A258682 .   30   900 |    90  .
%t A258682 a[n_]:=Module[{idn=IntegerDigits[n],idnn=IntegerDigits[n^2],idn1},
%t A258682 idn1=DeleteCases[idn,m_/;MemberQ[Complement[idn,idnn],m]];
%t A258682 Do[If[First[Position[idnn,idn1[[i]]]]!= {},idnn=Delete[idnn,First[Position[idnn,idn1[[i]]]]]],
%t A258682 {i,1,Length[idn1]}];FromDigits[idnn]]//Quiet;
%t A258682 a/@Range[0,56] (* _Ivan N. Ianakiev_, Jun 11 2015 *)
%o A258682 (Haskell)
%o A258682 import Data.List (delete)
%o A258682 a258682 n = read ('0' : minus (show (n ^ 2)) (show n)) :: Int  where
%o A258682    minus [] _  = []
%o A258682    minus us [] = us
%o A258682    minus (u:us) vs | elem u vs = minus us $ delete u vs
%o A258682                    | otherwise = u : minus us vs
%Y A258682 Cf. A000290, A029783, A189056, A178501.
%K A258682 nonn,base,look
%O A258682 0,3
%A A258682 _Reinhard Zumkeller_, Jun 07 2015