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A339921
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Numbers k such that 20^k + 3 is prime.
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1
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1, 5, 7, 13, 15, 18, 22, 61, 85, 208, 271, 898, 2142, 2856, 4392, 17171, 74886, 78901, 271951, 326600
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OFFSET
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1,2
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LINKS
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EXAMPLE
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1 is a term since 20^1 + 3 = 23 is a prime.
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MATHEMATICA
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Do[ If[ PrimeQ[ 20^n + 3], Print[n]], {n, 0, 100000}]
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PROG
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(PARI) is(n)=isprime(20^n + 3)
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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a(19)-a(20) correspond to probable primes discovered by Paul Bourdelais, Jan 06 2021
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STATUS
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approved
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