21433

Properties

Appears in sequences

• Sextan primes: p = (x^6 + y^6)/(x^2 + y^2).at n=28A002647
• a(n) = (5*n + 1)^2 + 4*n + 1.at n=29A007533
• T(2n,n-3), T given by A026747.at n=5A026860
• First term of strong prime sextets: p(m+1)-p(m) > p(m+2)-p(m+1) > p(m+3)-p(m+2) > p(m+4)-p(m+3) > p(m+5)-p(m+4).at n=4A054813
• Fifth term of weak prime sextet: p(m-3)-p(m-4) < p(m-2)-p(m-3) < p(m-1)-p(m-2) < p(m)-p(m-1) < p(m+1)-p(m).at n=6A054832
• Numbers k such that k, sigma(k) and phi(k) have the same decimal digits (ignoring multiplicity).at n=33A082059
• Primes whose decimal representation is a valid number in base 5 and interpreted as such is again a prime.at n=35A090708
• prime(k) for those k where floor((2*(prime(k+1)-prime(k))*PrimePi(k) mod (8*k))/k) = m with m = 10.at n=24A109564
• Primes p such that q-p = 34, where q is the next prime after p.at n=8A134116
• Primes congruent to 16 mod 59.at n=38A142743
• Primes congruent to 22 mod 61.at n=39A142820
• Triangle read by rows: T(n,k) is the number of odd permutations of {1,2,...,n} with no fixed points and having k excedances (n>=1; k>=1).at n=39A145880
• Triangle read by rows: T(n,k) is the number of odd permutations of {1,2,...,n} with no fixed points and having k excedances (n>=1; k>=1).at n=43A145880
• Primes p such that continued fraction of (1+sqrt(p))/2 has period 5 : primes in A146330.at n=37A146350
• List of primes of the form 25n^2-36n+13 with n>=0.at n=9A154354
• a(n) = 25*n^2 - 36*n + 13.at n=30A154355
• Hypotenuses of primitive Pythagorean triples in A195680 and A195681.at n=2A195682
• G.f.: Sum_{n>=0} (1+x)^n * Product_{k=1..n} ((1+x)^k - 1).at n=7A207556
• Primes p with property that there exists a number d>0 such that numbers p-k*d, k=1...7, are seven primes.at n=26A216590
• Strict Peak Primes: Smallest prime to have n strictly decreasing prime gaps on either side of a(n).at n=2A248703