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A090194
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Primes which when multiplied by their largest digit and 1 is added form another prime.
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1
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2, 43, 61, 263, 433, 461, 601, 641, 653, 661, 821, 857, 1061, 1063, 1187, 1361, 1423, 1487, 1613, 1811, 1871, 1877, 2063, 2081, 2143, 2161, 2621, 2801, 2837, 3061, 3163, 3581, 3623, 3631, 3643, 3851, 4561, 5087, 5261, 5381, 5623, 5807, 5861, 6011, 6053
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OFFSET
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1,1
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LINKS
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FORMULA
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In the prime sequence, select largest digit in each prime, multiply by the prime containing that digit, then add 1. If the result is another prime, add to sequence.
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EXAMPLE
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a(2)=43. Largest digit is 4. Multiply 43*4=172. 172+1=173, prime.
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MATHEMATICA
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Select[Prime[Range[1000]], PrimeQ[1+#*Max[IntegerDigits[#]]]&] (* Harvey P. Dale, May 21 2024 *)
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PROG
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(PARI) isok(p) = isprime(p) && isprime(p*vecmax(digits(p))+1); \\ Michel Marcus, Jun 08 2014
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CROSSREFS
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KEYWORD
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easy,nonn,base
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AUTHOR
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STATUS
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approved
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