A257085 - OEIS

%I #15 Feb 02 2016 02:54:21

%S 0,1,2,4,5,6,10,11,12,15,16,20,21,25,32,34,35,40,45,46,50,51,55,56,60,

%T 65,66,100,101,102,105,106,110,111,112,115,116,120,121,125,142,145,

%U 146,150,152,155,156,160,162,200,201,204,205,206,210,211,215,216,225,231,235,245,246,250,251,252,254,255,256

%N Numbers n such that the decimal expansions of both n and n^2 only use the digits 0..6.

%H Danny Rorabaugh, <a href="/A257085/b257085.txt">Table of n, a(n) for n = 1..10000</a>

%e 116 is in the list because 116 and 116^2 = 13456 do not use the digits 7, 8 or 9.

%e 182 is not in the list because it uses the digit 8 (even though 182^2 = 33124 would be fine).

%e 253 is not in the list because 253^2 = 6409 uses the digit 9.

%t Select[Range@ 256, Total@ Take[DigitCount[#], {7, 9}] == 0 && Total@ Take[DigitCount[#^2], {7, 9}] == 0 &] (* _Michael De Vlieger_, Apr 17 2015 *)

%o (PARI) isok(n) = ((vecmax(digits(n)) <= 6) && (vecmax(digits(n^2)) <= 6)) || (n==0); \\ _Michel Marcus_, Feb 02 2016

%Y Cf. A178501 (0..1), A136808(0..2), A136809(0..3), A136810 (0..4), A257086 (0..5).

%Y Cf. A136859, A256633.

%K nonn,easy,base

%O 1,3

%A _Danny Rorabaugh_, Apr 15 2015