21701

Properties

Appears in sequences

• Mersenne exponents: primes p such that 2^p - 1 is prime. Then 2^p - 1 is called a Mersenne prime.at n=24A000043
• McKay-Thompson series of class 23A for Monster.at n=28A058570
• Smallest prime divisor of (n-th primorial - (n+1)-st prime).at n=8A065314
• Mersenne prime exponents (A000043) which are also Sophie Germain primes (A005384).at n=5A065406
• Primes which can be represented as the sum of a triangular number and its reverse.at n=3A072386
• Numbers k such that k, sigma(k) and phi(k) have the same decimal digits (ignoring multiplicity).at n=35A082059
• Ordered hypotenuses of primitive Pythagorean triangles having legs that add up to a square.at n=21A088319
• Bisection of A000043.at n=12A099982
• Mersenne prime indices that are not Gaussian primes.at n=14A112634
• Primes p that divide Fibonacci[(p-1)/7].at n=29A125253
• Smallest prime p = n*m + 1 that divides m^m - 1 for some m > 1.at n=34A125556
• Primes of the form a^2 + b^2 + c^2 such that a^4 + b^4 + c^4 is prime as well and larger than the first one.at n=37A126118
• Primes p such that q = p+d (with d >= 6) is the next prime and both p and q are Sophie Germain primes.at n=36A128825
• McKay-Thompson series of class 23A for the Monster group with a(0) = 1.at n=28A134781
• Primes p1 such that p1^2+p2^3=pp are average of twin primes. p1 and p2 consecutive primes, p1 < p2.at n=21A138715
• Primes p such that 2^p-1 is prime and congruent to 31 mod 5!.at n=13A145040
• Primes p (A000043) such that 2^p-1 is prime (A000668) and congruent to 31 mod 6!.at n=9A145041
• Primes p of the form 4*k+1 for which s=26 is the least positive integer such that s*p-(floor(sqrt(s*p)))^2 is a square.at n=28A145050
• Base-2 logarithm of A136007(n)+1.at n=16A152961
• K-bit primes p such that p-2^i and p+2^i are composite for 0<=i<=K-1.at n=12A153352