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A129293
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Numbers m such that m^4-1 has no divisors d with 1 < d < m-1.
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5
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3, 4, 6, 150, 180, 240, 270, 420, 570, 1290, 1320, 2310, 2550, 2730, 3360, 3390, 4260, 4650, 5850, 5880, 6360, 6780, 9000, 9240, 9630, 10530, 10890, 11970, 13680, 13830, 14010, 14550, 16230, 16650, 18060, 18120, 18540, 19140, 19380, 21600, 21840, 23370
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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EXAMPLE
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{1,5,7,35,37,185,259,1295} is the set of divisors of 6^4-1, therefore 6 is a term, A129292(6) = #{1,3} = 2.
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PROG
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(PARI) is(k) = k == 3 || (isprime(k-1) && isprime(k+1) && isprime(k^2+1)); \\ Amiram Eldar, Apr 15 2024
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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