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A360656
Least k such that the decimal representation of 2^k contains all possible n-digit strings.
1
68, 975, 16963, 239697, 2994863
OFFSET
1,1
EXAMPLE
2^68 = 295147905179352825856 is the least power of 2 containing all ten decimal digits, so a(1) = 68 = A171744(1).
2^975 is the least power of 2 containing all 100 two-digit strings, so a(2) = 975.
PROG
(Python)
def a(n, starte=0):
e, p2, t = starte, 2**starte, 10**n
while True:
s2, ss = str(p2), set()
for i in range(len(s2)-n+1):
ss.add(s2[i:i+n])
if len(ss) == t:
return e
e += 1
p2 *= 2
print([a(n) for n in range(1, 4)]) # Michael S. Branicky, Feb 22 2023
CROSSREFS
Sequence in context: A250144 A250338 A223374 * A254645 A281049 A264316
KEYWORD
nonn,base,more
AUTHOR
Hans Havermann, Feb 15 2023
STATUS
approved