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A039935
Smallest k for which k, 2k, ... nk all contain the digit 4.
9
4, 24, 47, 471, 487, 1248, 1249, 6248, 6249, 6249, 12493, 12493, 12493, 12493, 12498, 31249, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 62499, 312497, 312497, 312497, 624984, 624984, 624984, 624984, 624984
OFFSET
1,1
LINKS
EXAMPLE
a(3) = 47 since 47, 94 and 141 all contain a 4.
PROG
(Python)
def aupton(terms):
k, n, alst = 1, 1, []
while len(alst) < terms:
while not all(str(i*k).count('4') > 0 for i in range(1, n+1)): k += 1
while str(n*k).count('4') > 0: alst.append(k); n += 1
k += 1
return alst[:terms]
print(aupton(39)) # Michael S. Branicky, Apr 24 2021
KEYWORD
base,nonn
EXTENSIONS
More terms from Patrick De Geest, Oct 15 1999
STATUS
approved