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A256630
Numbers n such that the decimal expansions of both n and n^2 have 0 as smallest digit and 4 as largest digit.
23
142201, 1422010, 11141110, 11411110, 11412021, 14220100, 20323421, 21024111, 101203421, 110141011, 110142201, 111411100, 114111100, 114120210, 120013421, 141433102, 142201000, 203234210, 210241110, 1012034210, 1101410011, 1101410110, 1101422010, 1114111000
OFFSET
1,1
MATHEMATICA
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 *)
PROG
(PARI) is(n) = vecmin(digits(n))==0 && vecmin(digits(n^2))==0 && vecmax(digits(n))==4 && vecmax(digits(n^2))==4
(Python)
from itertools import product
A256630_list = []
for l in range(11):
for a in ('1', '2', '3', '4'):
for b in product('01234', repeat = l):
for c in ('0', '1', '2'):
s = a+''.join(b)+c
if '0' in s and '4' in s:
n = int(s)
s2 = set(str(n**2))
if {'0', '4'} <= s2 <= {'0', '1', '2', '3', '4'}:
A256630_list.append(n)
print(A256630_list) # Chai Wah Wu, Apr 17 2015
CROSSREFS
Subsequence of A136810.
Sequence in context: A214479 A269321 A204287 * A263037 A086999 A175694
KEYWORD
nonn,base
AUTHOR
Felix Fröhlich, Apr 05 2015
EXTENSIONS
More terms from Alois P. Heinz, Apr 16 2015
STATUS
approved