20849

Properties

Appears in sequences

• a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (odd natural numbers), t = A000201 (lower Wythoff sequence).at n=41A025113
• Base 4 expansion of 1/n has equal percentage of each digit 0,1,2,3.at n=24A074709
• Base 4 expansion of 1/n has equal percentage of each digit 0,1,2,3 (primitive values of n only).at n=21A074900
• Fixed points when A001414 is iterated and started at factorials of prime numbers.at n=68A082086
• Primes congruent to 22 mod 59.at n=37A142749
• Primes such that when they are concatenated with their 10's complement (which also must be prime), the result is a brilliant number.at n=15A168466
• Smallest prime greater than n*(n+1)^2/2.at n=34A181956
• Primes which are the sum of two numbers of the form k*(k+1)^2/2.at n=40A210646
• Primes of the form 2*n^2+38*n+17.at n=38A243890
• Non-palindromic balanced primes in base 2.at n=40A256081
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 870", based on the 5-celled von Neumann neighborhood.at n=40A273705
• Primes for which the concatenation of the digits in the even positions and the concatenation of the digits in the odd positions are squares.at n=30A275797
• Upper ends of record gaps between numbers that are either prime or twice a prime.at n=13A290489
• a(n) is the smallest prime whose square is greater than the cube of a(n-1); a(1) = 2.at n=6A294148
• Number of n X 6 0..1 arrays with every element unequal to 0, 1, 3 or 8 king-move adjacent elements, with upper left element zero.at n=9A304219
• a(n) is the first prime p such that the concatenations of n consecutive primes, starting with p, in both forward and backward directions, are prime.at n=21A384958
• a(n) = A005117(A390138(n) + 1).at n=17A390241
• Prime numbersat n=2345