21997

Properties

Appears in sequences

• Primes that remain prime through 3 iterations of function f(x) = 5x + 2.at n=23A023283
• Primes that remain prime through 4 iterations of function f(x) = 5x + 2.at n=3A023313
• Primes p for which the period of reciprocal 1/p is (p-1)/12.at n=27A056217
• Number of base 13 circular n-digit numbers with adjacent digits differing by 9 or less.at n=4A125470
• Least positive integer k such that (n!)! + k is prime.at n=6A134056
• Primes congruent to 49 mod 59.at n=36A142776
• Primes p such that the multiplicative order of 2 modulo p is (p-1)/9.at n=14A152309
• Smaller member p of a pair (p,p+6) of consecutive primes in different centuries.at n=16A160370
• Number of lines through at least 2 points of a 10 X n grid of points.at n=31A160850
• Primes of the form floor(binomial(k,2)/4).at n=36A171574
• Least prime of the form x^2+13*n^2.at n=40A248409
• Number of (n+1) X (2+1) arrays of permutations of 0..n*3+2 with each element having directed index change 0,0 0,1 1,0 -1,0 or 0,-2.at n=4A264211
• T(n,k)=Number of (n+1)X(k+1) arrays of permutations of 0..(n+1)*(k+1)-1 with each element having directed index change 0,0 0,1 1,0 -1,0 or 0,-2.at n=19A264217
• Number of (5+1)X(n+1) arrays of permutations of 0..n*6+5 with each element having directed index change 0,0 0,1 1,0 -1,0 or 0,-2.at n=1A264222
• Square array read by antidiagonals upwards: M(n,k) is the initial occurrence of first prime p1 of consecutive primes p1, p2, where p2 - p1 = 2*k, and p1, p2 span a multiple of 10^n, n>=1, k>=1.at n=12A287050
• Start from the sequence of primes, keep the 1st, then delete 2 primes, keep the next, delete 3 primes, keep the next, delete 5 primes, etc ...at n=36A350170
• Primes p such that p+6, p-6, 2*p+3 and 2*p-3 are prime.at n=24A356079
• G.f. satisfies A(x) = 1 + x^5 / (1 - x*A(x)).at n=31A365698
• Prime numbersat n=2464