21317

Properties

Appears in sequences

• Primes of the form k^2 + 1.at n=26A002496
• Convolution of A000108 (Catalan) with A000351 (powers of 5).at n=6A046714
• Primes of form 4*p^2 + 1, p prime.at n=8A052292
• Odd powers of primes of the form q = x^2 + 1 (A002496).at n=35A054755
• Numbers whose divisors have the form m^k + 1, k>1.at n=28A054964
• a(n) = 4*prime(n)^2+1.at n=20A060429
• Primes of form n^2 + mu(n), where mu is A008683.at n=9A062459
• Primes p = product(A073692(n), A073692(n)+2,..., A073692(n+1)-2) plus 2.at n=29A073691
• Primes p such that the number of distinct prime divisors of all composite numbers between p and the next prime is 5.at n=33A075585
• Primes p such that all prime factors of p-1 have exponent 2.at n=12A089195
• Smallest member of a pair of consecutive twin prime pairs that have three primes between them.at n=28A089635
• Smallest prime p such that tau(p-1) + tau(p+1) is n, or 0 if no such number exists.at n=40A090482
• a(n) = floor(sqrt(a(n-1)^2 + a(n-2)^2)), a(1)=10, a(2)=30.at n=29A104863
• Divisorial primes: Primes p such that p = 1 + Product_{d|n} d for some n (ordered by n).at n=13A118370
• Expansion of (17-25*x-23*x^2+133*x^3)/(1-x)^4.at n=12A118587
• Numerators of partial sums of Catalan numbers scaled by powers of 1/5.at n=6A121002
• Primes of the form 4*k^2 + 1.at n=25A121326
• Primes in the sequence a(n)=n^2+3/2-1/2*(-1)^n.at n=40A125557
• Lower twin primes p1 such that p1-1 is a square.at n=8A145824
• Primes p such that continued fraction of (1 + sqrt(p))/2 has period 3.at n=44A146348