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