A090195 Primes which when multiplied by their largest digit and 1 is subtracted form another prime.

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

Harvey P. Dale, Table of n, a(n) for n = 1..1000

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

Adjacent sequences: A090192 A090193 A090194 * A090196 A090197 A090198

Keyword

easy,nonn,base

Author

Enoch Haga, Jan 22 2004

Status

approved