21787

Properties

Appears in sequences

• a(n) is the smallest prime p such that each of the first n primes has three cube roots mod p.at n=4A002225
• Concatenation of prime p and nextprime(p) is prime -> cycles of 2 steps possible.at n=4A036339
• Least prime in A031930 (lesser of 12-twins) whose distance to the next 12-twin is 2*n.at n=41A052355
• Partial sums of the partition function (A000041), with the last term subtracted. Also the sum of the row of the character table for S_n corresponding to the partition n-1,1 for n>1. Also the sum over all partitions lambda of n of one less than the number of 1's in lambda.at n=31A058884
• Primes with 23 as smallest positive primitive root.at n=9A061335
• Primes of the form perfect_power(n)+n.at n=22A075781
• Balanced primes of order six.at n=18A096698
• Primes of the form (prime(prime(k)) + prime(prime(k+1)))/2.at n=20A098042
• a(n) is the least prime for which the n-th term of the sequence S(a(n)) belongs to A007500, where each term of S(p) is the least prime >= the reversal of the previous term.at n=15A135436
• Primes congruent to 16 mod 59.at n=39A142743
• Number of subsets {x(1),x(2),...,x(k)} of {1,2,...,n} such that all differences |x(i)-x(j)| are distinct.at n=24A143823
• Primes p such that 8*p^2-2*p-1 divides Fibonacci(p).at n=19A159231
• Primes of the form 5n^2 + 7.at n=6A201485
• Primes p such that if q is the next prime after p then the concatenation of p with q and the concatenation of q with p are both primes.at n=35A225575
• Primes of the form 11*k^2-11*k+7.at n=20A267290
• Number of nX5 0..1 arrays with every element equal to 0, 1, 2, 4 or 6 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.at n=5A300934
• Number of nX6 0..1 arrays with every element equal to 0, 1, 2, 4 or 6 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.at n=4A300935
• T(n,k)=Number of nXk 0..1 arrays with every element equal to 0, 1, 2, 4 or 6 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.at n=49A300937
• T(n,k)=Number of nXk 0..1 arrays with every element equal to 0, 1, 2, 4 or 6 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.at n=50A300937
• Number of nX5 0..1 arrays with every element equal to 0, 1, 3, 4, 5 or 6 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.at n=5A301495