31753

Appears in sequences

• Strong pseudoprimes to base 53.at n=18A020279
• Strong pseudoprimes to base 77.at n=12A020303
• Strong pseudoprimes to base 88.at n=17A020314
• Numbers k such that the continued fraction for sqrt(k) has period 93.at n=26A020432
• Recurrence: a(n) = Sum_{k=0..n-1} C(2*n-1,n-k-1)*a(k) with a(0)=1.at n=7A110531
• Heptagonal numbers with only odd digits.at n=9A117993
• a(n) = 18*n^2 + 1.at n=41A157889
• a(n) = 72*n^2 + 1.at n=21A158740
• Number of zero-sum n X n -1..1 arrays with every element unequal to at most two horizontal and vertical neighbors.at n=3A202040
• Number of zero-sum nX4 -1..1 arrays with every element unequal to at most two horizontal and vertical neighbors.at n=3A202043
• T(n,k)=Number of zero-sum nXk -1..1 arrays with every element unequal to at most two horizontal and vertical neighbors.at n=24A202047
• Heptagonal numbers (A000566) that are semiprimes (A001358).at n=21A259676
• Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where A(n,k) is Sum_{j=0..floor(n/2)} ((n-j)!/j!)*binomial(n-j,j)*k^(n-2*j).at n=59A305401
• a(n) is the smallest k such that (Z/kZ)* contains C_(2n) X C_(2n) as a subgroup, where (Z/kZ)* is the multiplicative group of integers modulo n.at n=27A307436
• a(n) = prime(n) * prime(2n).at n=29A319613
• Nonprime Heinz numbers of multiples of triangular partitions, or of finite arithmetic progressions with offset 0.at n=40A325407
• Heptagonal numbers (A000566) with prime indices (A000040).at n=29A346494
• Number of integer compositions of n into odd parts covering an initial interval of odd positive integers.at n=24A356604