cp's OEIS Frontend

A256630 Numbers n such that the decimal expansions of both n and n^2 have 0 as smallest digit and 4 as largest digit.

%I A256630 #28 Apr 11 2020 05:29:46
%S A256630 142201,1422010,11141110,11411110,11412021,14220100,20323421,21024111,
%T A256630 101203421,110141011,110142201,111411100,114111100,114120210,
%U A256630 120013421,141433102,142201000,203234210,210241110,1012034210,1101410011,1101410110,1101422010,1114111000
%N A256630 Numbers n such that the decimal expansions of both n and n^2 have 0 as smallest digit and 4 as largest digit.
%H A256630 Chai Wah Wu, <a href="/A256630/b256630.txt">Table of n, a(n) for n = 1..10000</a>
%t A256630 fQ[n_] := Block[{c = DigitCount@ n}, And[Plus @@ Take[c, {5, 9}] == 0, c[[4]] > 0, c[[10]] > 0]]; Select[Range@ 10000000, fQ@ # && fQ[#^2] &] (* _Michael De Vlieger_, Apr 12 2015 *)
%o A256630 (PARI) is(n) = vecmin(digits(n))==0 && vecmin(digits(n^2))==0 && vecmax(digits(n))==4 && vecmax(digits(n^2))==4
%o A256630 (Python)
%o A256630 from itertools import product
%o A256630 A256630_list = []
%o A256630 for l in range(11):
%o A256630     for a in ('1','2','3','4'):
%o A256630         for b in product('01234',repeat = l):
%o A256630             for c in ('0','1','2'):
%o A256630                 s = a+''.join(b)+c
%o A256630                 if '0' in s and '4' in s:
%o A256630                     n = int(s)
%o A256630                     s2 = set(str(n**2))
%o A256630                     if {'0','4'} <= s2 <= {'0','1','2','3','4'}:
%o A256630                         A256630_list.append(n)
%o A256630 print(A256630_list) # _Chai Wah Wu_, Apr 17 2015
%Y A256630 Cf. A256631, A256633, A256634, A256708, A256709, A256889.
%Y A256630 Subsequence of A136810.
%K A256630 nonn,base
%O A256630 1,1
%A A256630 _Felix Fröhlich_, Apr 05 2015
%E A256630 More terms from _Alois P. Heinz_, Apr 16 2015