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

0, 0, 4, 9, 16, 2, 3, 49, 64, 81, 0, 2, 44, 69, 96, 22, 25, 289, 324, 36, 40, 44, 484, 59, 576, 6, 76, 9, 74, 841, 90, 96, 104, 1089, 1156, 122, 129, 169, 1444, 1521, 160, 681, 176, 189, 1936, 202, 211, 2209, 230, 201, 20, 260, 704, 2809, 2916, 302, 313

Offset: 0

Author

Reinhard Zumkeller, Jun 07 2015

Keywords

• nonn
• base
• look

Comments

a(A029783(n)) = A029783(n)^2; a(A189056(n)) < A189056(n)^2;

a(A178501(n)) = 0.

Examples

			.    n   n^2 |  a(n)
. -----------+------
.   20   400 |    40
.   21   441 |    44
.   22   484 |   484
.   23   529 |    59
.   24   576 |   576
.   25   625 |     6
.   26   676 |    76  not 67, as digits of n are to be removed
.   27   729 |     9                                  from left to right
.   28   784 |    74
.   29   841 |   841
.   30   900 |    90  .
		

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A000290, A029783, A189056, A178501.

Programs

Haskell

import Data.List (delete)
a258682 n = read ('0' : minus (show (n ^ 2)) (show n)) :: Int  where
   minus [] _  = []
   minus us [] = us
   minus (u:us) vs | elem u vs = minus us $ delete u vs
                   | otherwise = u : minus us vs

Mathematica

a[n_]:=Module[{idn=IntegerDigits[n],idnn=IntegerDigits[n^2],idn1},
idn1=DeleteCases[idn,m_/;MemberQ[Complement[idn,idnn],m]];
Do[If[First[Position[idnn,idn1[[i]]]]!= {},idnn=Delete[idnn,First[Position[idnn,idn1[[i]]]]]],
{i,1,Length[idn1]}];FromDigits[idnn]]//Quiet;
a/@Range[0,56] (* Ivan N. Ianakiev, Jun 11 2015 *)