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

Author

Enoch Haga, Jan 22 2004

Keywords

• easy
• nonn
• base

Examples

			a(2)=41. Largest digit is 4. Multiply 41*4=164. 164-1=163, prime.
		

Links

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

Crossrefs

Cf. A060418.

Programs

Mathematica

Select[Prime[Range[1000]],PrimeQ[# Max[IntegerDigits[#]]-1]&] (* Harvey P. Dale, Dec 31 2019 *)

PARI

isok(p) = isprime(p) && isprime(p*vecmax(digits(p))-1); \\ Michel Marcus, Jun 08 2014

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.