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A035059
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Numbers k such that 2^k does not contain the digit 4 (probably finite).
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1
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0, 1, 3, 4, 5, 7, 8, 9, 13, 15, 16, 17, 21, 23, 24, 29, 40, 41, 43, 55, 69, 75, 85, 107
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OFFSET
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1,3
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COMMENTS
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LINKS
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MATHEMATICA
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Join[{0}, Select[Range@10000, FreeQ[IntegerDigits[2^#], 4] &]] (* Vincenzo Librandi, May 07 2015 *)
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PROG
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(Magma) [n: n in [0..1000] | not 4 in Intseq(2^n) ]; // Vincenzo Librandi, May 07 2015
(Python)
N = 200; modder = 10**N; REPORT = 10**5
def ok(s): return '4' not in s
def ok1(n): return ok(str(pow(2, n, modder)))
def afind(limit, startk=0, verbose=False):
full_tests = 0
for k in range(startk, limit):
if ok1(k):
full_tests += 1
if ok(str(pow(2, k))): print(k, end=", ")
if verbose and k and k%REPORT == 0:
print("[ ...", k, full_tests, "]")
k += 1
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CROSSREFS
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Cf. similar sequences listed in A035064.
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KEYWORD
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nonn,base,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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