21211

Properties

Appears in sequences

• Primes that contain digits 1 and 2 only.at n=7A020450
• Primes that remain prime through 3 iterations of function f(x) = 8x + 5.at n=20A023293
• Primes p such that p+1 is palindromic.at n=30A028981
• Primes having only {0, 1, 2} as digits.at n=22A036953
• Numerators of continued fraction convergents to sqrt(885).at n=6A042710
• Discriminants of imaginary quadratic fields with class number 19 (negated).at n=37A046016
• Primes of form 210*p + 1 where p is a prime.at n=16A051648
• Numbers k such that A048138(k) is a prime and sets a new record for such primes.at n=36A064440
• The zero-free, right-to-left factorial walk encoding for each rooted plane tree encoded by A014486. Sequence A071155 shown with factorial expansion (A007623).at n=29A071157
• Factorial expansion of A071156.at n=38A071158
• Primes of form 4k+3 written in base 3.at n=24A072805
• Left-to-right binary enumeration.at n=35A081242
• Primes whose decimal representation also represents a prime in base 3.at n=9A089981
• Primes arising as A093929(n)*A093929(n+1)+2.at n=31A093930
• a(n) is the 6th term in Euclid-Mullin (EM) prime sequence initiated with n-th prime.at n=25A094462
• Number of different rectangles created when a square sheet of paper is folded n times, the first time by one of the diagonals of the square and after by the median of the triangle.at n=8A097405
• Primes with maximal digit = 2.at n=19A106100
• Primes with digital product = 4.at n=5A107690
• Numbers with digits 1 and 2 and at least one of each.at n=41A111066
• Number of partitions of {1,..,n} into any number of lists of size not equal to 2, where a list means an ordered subset, cf. A000262.at n=7A113235