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A096681
Least k such that decimal representation of k*n contains only digits 0 and 2.
18
2, 1, 74, 5, 4, 37, 286, 25, 24691358, 2, 2, 185, 154, 143, 148, 125, 1306, 12345679, 1158, 1, 962, 1, 9574, 925, 8, 77, 81563786, 715, 75938, 74, 7162, 625, 6734, 653, 572, 61728395, 6, 579, 518, 5, 542, 481, 51214, 5, 49382716, 4787, 426, 4625, 44898, 4
OFFSET
1,1
LINKS
FORMULA
a(n) = A078241(n)/n.
PROG
(PARI) isok(n) = my(vd = vecsort(digits(n), , 8)); (vd == [0, 2]) || (vd == [2]);
a(n) = my(k=1); while(!isok(k*n), k++); k; \\ Michel Marcus, Sep 25 2016
(Python)
def next02(n):
s = str(n)
if s > '2'*len(s): return int('2' + '0'*len(s))
for i, c in enumerate(s):
if c == '1': return int(s[:i] + '2' + '0'*(len(s)-i-1))
elif s[i:] > '2'*(len(s)-i): return int(s[:i-1] + '2' + '0'*(len(s)-i))
def a(n):
k = 1
while set(str(k*n)) - set('02') != set(): k = max(k+1, next02(k*n)//n)
return k
print([a(n) for n in range(1, 51)]) # Michael S. Branicky, Feb 01 2021
KEYWORD
base,nonn
AUTHOR
Ray Chandler, Jul 12 2004
STATUS
approved