1020101

Properties

Appears in sequences

• a(1)=5, a(n) is the smallest prime dividing 4*Q^2 + 1 where Q is the product of all previous terms in the sequence.at n=2A057207
• Primes p such that sigma(p-1)+sigma(p+1) is prime.at n=20A067464
• Primes of the form n^2*totient(n)+1 (or A053191(n) + 1).at n=29A076669
• a(n) is the largest prime of the form x^2 + 1 <= 2^n.at n=19A083849
• Primes of the form 12*k + 5 generated recursively. Initial prime is 5. General term is a(n) = Min_{p is prime; p divides 1 + 4*Q^2; p == 5 (mod 12)}, where Q is the product of previous terms in the sequence.at n=2A124986
• a(n) is the least n-digit prime p whose reversal is a prime q < p.at n=5A152033
• Primes p such that the reversal of p is prime and the product of p with its reversal is a palindrome.at n=10A161721
• Primes of the form 1+A162143(k).at n=16A164517
• Primes of the form (10p)^2 + 1, where p is also prime.at n=8A179293
• The smallest prime p such that tau(p-1) + tau(p+1) = prime(n), or 0 if no such prime exists; where tau(k) is the number of divisors of k.at n=16A189536
• Primes such that the sum of the squares of their digits equals the number of their digits.at n=7A199169
• Palindromic primes in the sense of A007500 with digits '0', '1' and '2' only.at n=13A199302
• Base 2i representation of negative integers.at n=34A212542
• a(0) = 1; for n > 0, a(n) = 1 + 4*Product_{i=1..n-1} a(i)^2.at n=3A231830
• a(n) = ( a(n-1)^2*a(n-2)^2*a(n-3)^2 + 1 ) / a(n-4), with a(0)=a(1)=a(2)=a(3)=1.at n=7A276267
• Primes which divide a term of A073935.at n=18A286499
• Odd integers k such that 3^((k-1)/2) + 1 == 0 (mod k*(k-1)/2).at n=3A337828
• Odd integers k such that 7^((k-1)/2) + 1 == 0 (mod k*(k-1)/2).at n=3A337831
• Emirps p such that p, its digit reversal, and their squares are all quasi-Niven numbers.at n=12A356979
• Prime numbersat n=79982