20689

Appears in sequences

• Pseudoprimes to base 78.at n=38A020206
• Number of 4X2 integer matrices with each row summing to zero, row elements in nondecreasing order, rows in lexicographically nondecreasing order, and the sum of squares of the elements <= 2*n^2 (number of collections of 4 zero-sum 2-vectors with total modulus squared not more than 2*n^2, ignoring vector and component permutations).at n=32A192703
• Number of nX6 arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2.at n=2A221386
• T(n,k)=Number of nXk arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2.at n=30A221388
• Number of 3 X n arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2.at n=5A221389
• a(1) = 1; for n > 1, a(n) is the smallest positive integer that has not yet appeared which contains all the distinct digits of the sum of all previous terms a(1)..a(n-1).at n=46A368347
• a(n) is the 2-adic valuation of 1 + 3*{the n-th iterate of 27 with A371094}.at n=13A372448
• Integers k such that 2047*2^k - 1 is prime.at n=13A387927