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A254928
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Smallest (nontrivial) prime that, for each k from 2 to n, remains prime when each digit is replaced by the digit's k-th power.
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0
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OFFSET
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2,1
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COMMENTS
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Examples of trivial primes are 11, 101, etc, i.e., all primes in the sequence A020449: these generate themselves for all powers. These primes are excluded, otherwise all terms would be 11 since sequence wants smallest primes.
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LINKS
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EXAMPLE
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a(5) = 137; (1^k)&(3^k)&(7^k), where "&" represents concatenation of numbers:
for k=2, 1949 (prime), for k=3, 127343 (prime),
for k=4, 1812401 (prime), for k=5, 124316807 (prime).
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CROSSREFS
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Cf. A020449 (primes that contain digits 0 and 1 only).
Cf. A068492 (primes that remain prime after each digit is replaced by its square).
Cf. A048393 (replacing digits d in decimal expansion of n with d^3 yields a prime).
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KEYWORD
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nonn,base,hard,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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