OFFSET
1,1
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..1000 (n = 71..178 from Giovanni Resta)
MATHEMATICA
fQ[n_] := Block[{d = DigitCount@ n}, Plus @@ Join[Take[d, {1, 2}], Take[d, {8, 10}]] == 0 && d[[3]] > 0 && d[[7]] > 0]; Select[Range@ 1000000, fQ@# && fQ[#^2] &] (* Michael De Vlieger, Apr 27 2015 *)
PROG
(PARI) is(n) = vecmin(digits(n))==3 && vecmin(digits(n^2))==3 && vecmax(digits(n))==7 && vecmax(digits(n^2))==7
(Python)
from itertools import product, repeat
A257486_list = []
for l in range(12):
....for a in product('34567', repeat = l):
........for b in ('4', '5', '6'):
............s = ''.join(a)+b
............if '3' in s and '7' in s:
................n = int(s)
................if {'3', '7'} <= set(str(n**2)) <= {'3', '4', '5', '6', '7'}:
....................A257486_list.append(n) # Chai Wah Wu, May 02 2015
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Felix Fröhlich, Apr 26 2015
EXTENSIONS
a(22)-a(26) from Hiroaki Yamanouchi, May 03 2015 (using Chai Wah Wu's b-file)
STATUS
approved