21881

Properties

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has period 89.at n=22A020428
• Starting index of a string of 4 or more consecutive equal digits in decimal expansion of Pi.at n=20A049516
• Starting index of a string of exactly 4 consecutive equal digits in decimal expansion of Pi.at n=13A049520
• Fourth term of weak prime sextet: p(m-2)-p(m-3) < p(m-1)-p(m-2) < p(m)-p(m-1) < p(m+1)-p(m) < p(m+2)-p(m+1).at n=8A054831
• Primes p whose reciprocal has period (p-1)/10.at n=30A056215
• Starting positions of strings of three 6's in the decimal expansion of Pi.at n=15A083625
• Prime numbers p such that primepi(p) + p is a square.at n=17A104269
• Smallest prime in kx^3+x+2 is prime.at n=14A114366
• Primes congruent to 51 mod 59.at n=37A142778
• Primes congruent to 43 mod 61.at n=38A142841
• Middle of 3 consecutive prime numbers, p1, p2, p3, such that p1*p2*p3*d1*d2 = average of twin prime pairs; d1 (delta) = p2 - p1, d2 (delta) = p3 - p2.at n=19A153410
• Smallest primes p = p(k) with (p(k)+p(k+1)+p(k+2))/15 an integer.at n=15A168556
• Primes p such that 2*p^3-+15 are also prime.at n=28A174364
• Triangle of coefficients of polynomials v(n,x) jointly generated with A209773; see the Formula section.at n=53A209774
• The number of simple permutations of length n in a particular geometric grid class.at n=19A226432
• Number of magic labelings with magic sum n of first graph shown in link.at n=11A244869
• Primes of form n^2 + 10000.at n=20A256838
• A set of nine consecutive primes forming a 3 X 3 semimagic square with the smallest magic constant (65573).at n=7A265614
• Numbers of closed lambda terms of natural size n.at n=13A275057
• a(0) = 1, a(1) = 2; for n>1, a(n) = a(n-1) + a(n-2) + floor(n/2).at n=19A281362