19951
domain: N
Appears in sequences
- Fermat pseudoprimes to base 2, also called Sarrus numbers or Poulet numbers.at n=35A001567
- a(n) = a(n-1) + 7*a(n-2), a(0)=0, a(1)=1.at n=10A015442
- Pseudoprimes to base 35.at n=38A020163
- Pseudoprimes to base 63.at n=38A020191
- Pseudoprimes to base 90.at n=31A020218
- Strong pseudoprimes to base 4.at n=15A020230
- Strong pseudoprimes to base 50.at n=14A020276
- Strong pseudoprimes to base 58.at n=18A020284
- Strong pseudoprimes to base 64.at n=42A020290
- Strong pseudoprimes to base 70.at n=17A020296
- Strong pseudoprimes to base 79.at n=19A020305
- Strong pseudoprimes to base 86.at n=8A020312
- Strong pseudoprimes to base 90.at n=10A020316
- Strong pseudoprimes to base 98.at n=22A020324
- Discriminants of quintic fields with 2 complex conjugates (negated).at n=34A023684
- Odd 10-gonal (or decagonal) numbers.at n=35A028993
- Super-Poulet numbers: Poulet numbers whose divisors d all satisfy d|2^d-2.at n=16A050217
- Composite numbers k which divide A001045(k-1).at n=28A066488
- Pseudoprimes whose prime factors do not divide any smaller pseudoprime.at n=6A084653
- For p = prime(n), a(n) is the smallest base-2 pseudoprime N (that is, 2^(N-1) = 1 mod N) such that p divides N.at n=18A085999