21023

Properties

Appears in sequences

• a(n) = [ a(n-1)/a(1) ] + [ a(n-3)/a(3) ] + [ a(n-5)/a(5) ] + ..., for n >= 3.at n=37A022878
• Primes that remain prime through 3 iterations of function f(x) = 3x + 4.at n=13A023278
• Primes of the form k^2 - 2.at n=35A028871
• Numerators of continued fraction convergents to sqrt(429).at n=7A041816
• Row sums of triangle A054453.at n=14A054455
• Primes that are 2 less than a perfect power m^k, k >= 2.at n=39A094786
• Smallest prime ending in prime(n) and == 1 (mod prime(n)), or 0 if no such prime exists.at n=8A096069
• Primes congruent to 39 mod 61.at n=36A142837
• Depression-type primes with five digits; from left to right digits decrease to and increase from the central digit.at n=3A157083
• Primes p such that all the digits needed to write the consecutive Primes from 2 to p fill exactly a square (no holes, no overlaps).at n=26A158024
• Primes that are the sum of three consecutive primes in A034962.at n=31A207527
• Triangle read by rows: T(n,k) is the k-th generalized Eulerian number of order n and degree 4, n >= 1.at n=48A211234
• Numbers n such that Q(sqrt(n)) has class number 9.at n=32A218041
• a(n+1) is the smallest prime > a(n) such that the digits of a(n) are all (with multiplicity) contained in the digits of a(n+1), with a(1)=2.at n=10A242904
• Prime p such that sqrt(p+2) is semiprime (A001358).at n=12A257933
• a(1)=a(2)=1, a(n) = ceiling(e*a(n-1) - a(n-2)) for n>2.at n=13A258898
• Table read by rows: list of prime 5-tuples of the form (p, p+2, p+6, p+8, p+12).at n=34A270998
• Primes equal to a heptagonal number plus 1.at n=23A285791
• Primes equal to a centered heptagonal number plus 1.at n=15A285811
• Primes in A239237.at n=13A361252