21193

Properties

Appears in sequences

• Fibonacci sequence beginning 4, 19.at n=16A022135
• Primes p such that the decimal digits of p^2 can be partitioned into two or more nonzero squares.at n=39A048646
• Class 6+ primes.at n=25A081634
• Let p = prime(sigma(n)) and q = prime(phi(n)), then p is in the sequence if p-q = 6.at n=26A103176
• Poincaré series [or Poincare series] P(C#_{4,2}; x).at n=14A124631
• Numbers k such that k and k^2 use only the digits 1, 2, 3, 4 and 9.at n=17A136972
• Primes congruent to 26 mod 61.at n=32A142824
• 50k^2-40k-17 interleaved with 50k^2+10k+13 for k=>0.at n=42A217893
• Array: each row starts with the least prime not in a previous row, and each prime p in a row is followed by the greatest prime < 3*p.at n=47A229609
• Primes p such that 2*prime(p) + 1 = prime(q) for some prime q.at n=24A261361
• Numbers n such that n!3 + 3^9 is prime, where n!3 = n!!! is a triple factorial number (A007661).at n=43A265378
• Twin primes p such that the absolute difference of p and the reverse of its twin is a twin prime.at n=38A342216
• a(n) = A119435(2^n).at n=32A353035
• a(n) is the numerator of Sum_{k = 0..n} fusc(k)/fusc(k+1) (where fusc is Stern's diatomic series A002487).at n=20A355075
• Prime numbersat n=2384