21019

Properties

Appears in sequences

• Primes of the form n^2 - 6.at n=23A028880
• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 90 ones.at n=17A031858
• Number of partitions of n into parts not of the form 19k, 19k+9 or 19k-9. Also number of partitions with at most 8 parts of size 1 and differences between parts at distance 8 are greater than 1.at n=39A035978
• a(1) = 2, a(2) = 3; for n > 0, a(n+2) is the smallest prime chosen so that (a(n+2) - a(n+1))/(a(n+1) - a(n)) is an integer.at n=18A084736
• Last term of prime quadruples.at n=19A090258
• Largest prime of the set of four consecutive primes whose sum of digits is a set of four distinct primes.at n=34A106818
• Least odd prime a(n) such that (a(n)*M(n))^2 + a(n)*M(n) - 1 is prime with M(n) = Mersenne-primes (A000043).at n=25A107709
• Greatest prime divisor of A114599(n), or 1 if A114599(n) = 1.at n=17A114600
• Primes congruent to 15 mod 59.at n=37A142742
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (-1, 1, 0), (0, 1, -1), (0, 1, 1), (1, 0, 0)}.at n=8A150176
• a(1) = 1; thereafter a(n) is always the smallest integer > a(n-1) not leading to a contradiction, such that any five consecutive digits in the sequence sum up to a prime.at n=32A152605
• Primes p such that (p-1)*p*(p+1)-p+2 and (p-1)*p*(p+1)+p-2 are primes.at n=32A154944
• Depression-type primes with five digits; from left to right digits decrease to and increase from the central digit.at n=2A157083
• Primes obtained from other primes by pre-concatenating with 2.at n=37A165243
• Primes in A105720.at n=8A166619
• Primes of the form p(i)*p(i+1)+p(i+2)+p(i+3) where p(i) is a prime.at n=14A180947
• Primes p such that p - 2 and p^3 - 2 are also prime.at n=46A240126
• Greater of twin primes of (40n-23,40n-21).at n=27A244505
• Table read by rows: list of prime 5-tuples of the form (p, p+2, p+6, p+8, p+12).at n=33A270998
• Twin primes p such that the absolute difference of p and the reverse of its twin is a twin prime.at n=36A342216