Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 4500 articles have referenced us, often saying "we would not have discovered this result without the OEIS".
A023327
Numbers n such that n remains prime through 4 iterations of function f(x) = 9x + 10.
(MAGMA) [n: n in [1..5000000] | IsPrime(n) and IsPrime(9*n+10) and IsPrime(81*n+100) and IsPrime(729*n+910) and IsPrime(6561*n+8200)] [From Vincenzo Librandi, Aug 04 2010]