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A090195
Primes which when multiplied by their largest digit and 1 is subtracted form another prime.
1
2, 41, 163, 181, 211, 431, 463, 613, 653, 853, 1163, 1381, 1483, 1613, 1801, 1861, 1873, 2011, 2063, 2141, 2221, 2243, 2411, 2633, 2851, 3041, 3181, 3583, 3623, 4211, 4241, 4363, 4421, 4463, 4483, 4603, 5563, 5581, 5821, 5851, 6113, 6143, 6203, 6553
OFFSET
1,1
LINKS
FORMULA
In the prime sequence, select largest digit in each prime, multiply by the prime containing that digit, then subtract 1. If the result is another prime, add to sequence.
EXAMPLE
a(2)=41. Largest digit is 4. Multiply 41*4=164. 164-1=163, prime.
MATHEMATICA
Select[Prime[Range[1000]], PrimeQ[# Max[IntegerDigits[#]]-1]&] (* Harvey P. Dale, Dec 31 2019 *)
PROG
(PARI) isok(p) = isprime(p) && isprime(p*vecmax(digits(p))-1); \\ Michel Marcus, Jun 08 2014
CROSSREFS
Cf. A060418.
Sequence in context: A047936 A007533 A088565 * A287335 A212837 A063271
KEYWORD
easy,nonn,base
AUTHOR
Enoch Haga, Jan 22 2004
STATUS
approved