21493

Properties

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has period 51.at n=35A020390
• a(n) = floor(a(n-1)/(sqrt(5) - 2)) for n > 0 and a(0) = 1.at n=7A024551
• Expansion of 1/((1-2x)(1-3x)(1-4x)(1-9x)).at n=4A025470
• Number of compositions (ordered partitions) of n into distinct parts >= 2.at n=34A032022
• Third member of a sexy prime quadruple: value of p+12 such that p, p+6, p+12 and p+18 are all prime.at n=36A046123
• Let (p1,p2), (p3,p4) be pairs of twin primes with p1*p2=p3+p4-1; sequence gives values of p2.at n=22A047977
• Sixth term of strong prime sextets: p(m-4)-p(m-5) > p(m-3)-p(m-4) > p(m-2)-p(m-3) > p(m-1)-p(m-2) > p(m)-p(m-1).at n=4A054818
• Numbers n such that [A070080(n), A070081(n), A070082(n)] is an isosceles integer triangle with integer area.at n=32A070145
• Primes of the form perfect_power(n)+n.at n=21A075781
• Primes p such that p+1, p+2 and p+3 have equal number of divisors.at n=25A119711
• Primes p such that p+1, p+2, p+3 and p+4 have equal number of divisors.at n=3A119728
• Primes p such that p+1, p+2, p+3, p+4 and p+5 have equal number of divisors.at n=2A119730
• A linear recurrence sequence: a(n) = a(n-1) + a(n-3) + a(n-5) + a(n-6).at n=24A128429
• Primes p such that p^3 - 24 and p^3 + 24 are also primes.at n=37A153323
• A000110 / A014182: (A154107 convolved with A014182 = Bell numbers).at n=9A154107
• Primes p such that A000041(p)+p are also prime numbers.at n=15A163151
• Row sums of A208657.at n=10A208658
• Primes dividing nonzero terms in A003095: the iterates of x^2 + 1 starting at 0.at n=45A247981
• Prime numbers p such that p^3 is an interprime = average of two successive primes.at n=32A248799
• Primes of the form k!6-12, where k!6 is the sextuple factorial number (A085158).at n=2A289730