21859

Properties

Appears in sequences

• a(n) = Sum_{i=0..n} Sum_{j=0..n} T(i,j), T given by A026747.at n=12A026756
• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 94 ones.at n=25A031862
• First term of weak prime sextet: p(m+1)-p(m) < p(m+2)-p(m+1) < p(m+3)-p(m+2) < p(m+4)-p(m+3) < p(m+5)-p(m+4).at n=8A054828
• Primes p such that the sum of the digits of p is not prime, but the sum of each digit raised to the 4th power is prime.at n=17A091368
• Indices of Fibonacci numbers in Stern's diatomic series A049456 regarded as a single linear sequence.at n=14A094968
• a(n) = floor(9^n/5^n).at n=17A094986
• Primes that do not divide any term of the Lucas 4-step sequence A073817.at n=21A106300
• Sum of primes p with n^2 < p < (n+1)^2.at n=43A108314
• a(n) = 6 + floor( Sum_{j=1..n-1} a(j)/4 ).at n=37A120164
• Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0) and consisting of n steps taken from {(-1, -1), (-1, 0), (0, 1), (1, 0), (1, 1)}.at n=7A151316
• a(1) = 2. Let k >= 1 be the minimal integer such that 2*k*a(n-1) + 1 has at least one prime divisor which is not already in the sequence. Then a(n) is the smallest such divisor.at n=55A174162
• Sum of tail length of S over all 2^n strings S consisting of n 2's and 3's.at n=12A216813
• Number of partitions of n such that the number of even parts is a part and the number of odd parts is a part.at n=49A240575
• Number of nX5 0..3 arrays with no element equal to one plus the sum of elements to its left or zero plus the sum of elements above it or zero plus the sum of the elements diagonally to its northwest or zero plus the sum of the elements antidiagonally to its northeast, modulo 4.at n=5A240759
• T(n,k)=Number of nXk 0..3 arrays with no element equal to one plus the sum of elements to its left or zero plus the sum of the elements above it or zero plus the sum of the elements diagonally to its northwest or zero plus the sum of the elements antidiagonally to its northeast, modulo 4.at n=50A240760
• a(n) = position of the first occurrence of n in A245714.at n=32A245723
• a(n) = floor((3/sqrt(5))^n).at n=34A255216
• A set of nine consecutive primes forming a 3 X 3 semimagic square with the smallest magic constant (65573).at n=4A265614
• Let F(g,p) be the frequency of g up to prime nextprime(p+1). Primes p such that F(2,p) = F(4,p) and g = 2 or 4.at n=43A274122
• a(n) is the first prime p such that the sum of 2*n consecutive primes starting at p is (q-1)*q where q is prime, or 0 if there is no such p.at n=7A338990