21247

Properties

Appears in sequences

• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 80 ones.at n=21A031848
• Trisection of A007294.at n=39A073472
• Prime numbers, isolated from neighboring primes by >16.at n=23A137875
• Primes congruent to 7 mod 59.at n=37A142734
• Primes congruent to 19 mod 61.at n=38A142817
• 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, 0, 0), (-1, 1, 1), (0, -1, 1), (0, 0, 1), (1, 0, -1)}.at n=10A148323
• Prime numbers with gaps larger than 18 towards both neighboring primes.at n=11A163111
• Primes that are the sum of three consecutive primes in A034962.at n=32A207527
• Start with a single hexagon; at n-th generation add a hexagon at each expandable vertex (this is the "vertex to side" version); a(n) is the sum of all label values at n-th generation. (See comment for construction rules.)at n=18A247905
• Positions of records in A166133.at n=37A256404
• Numbers n such that A166133(n) sets a new record and also satisfies A166133(n)=A166133(n-1)^2-1.at n=22A256422
• Lexicographically largest strictly increasing sequence of primes for which the continued square root map produces Feigenbaum's constant delta = 4.6692016... (A006890).at n=26A257809
• Primes of the form 8*n^2+8*n+31.at n=38A289839
• Primes P where the distance to the nearest prime is greater than 2*log(P).at n=17A330426
• Numbers k such that k and k+4 are consecutive cubefree numbers.at n=8A349235
• Index in A353715 of the first term divisible by 2^n and no higher power of 2, or -1 if no such term exists.at n=10A353727
• Primes whose product of nonzero digits divided by the sum of its digits is also prime.at n=38A371631
• Number of integer compositions of n that are the first sums of some composition.at n=27A391683
• Prime numbersat n=2388