21307

Appears in sequences

• Quasi-Carmichael numbers to base 7: squarefree composites n such that (n,2*3*5) = 1 and prime p|n ==> p-7|n-7.at n=4A029556
• Numbers n such that 121*2^n-1 is a prime.at n=16A050586
• Record-setting differences between adjacent elements of the Mian-Chowla sequence A005282.at n=39A080222
• Numbers k such that (k / sum of digits of k) and (k+1 / sum of digits of k+1) are both semiprime.at n=37A085774
• a(n) = numerator of constant lambda(n) involved in a recurrence for the Atkin polynomials A_k(j).at n=24A145226
• a(n) + a(n+1) + a(n+2) = n^3.at n=41A152728
• a(n) = b(n) + b(n+1) + 2, where b() = A000930().at n=25A170934
• Fourth accumulation array, T, of the natural number array A000027, by antidiagonals.at n=56A185509
• Irregular array T(n,k) of the numbers of non-extendable (complete) non-self-adjacent simple paths incorporating each of a minimal subset of nodes within a square lattice bounded by rectangles with nodal dimensions n and 5, n >= 2.at n=30A214563
• Irregular array T(n,k) of the numbers of non-extendable (complete) non-self-adjacent simple paths incorporating each of a minimal subset of nodes within a square lattice bounded by rectangles with nodal dimensions n and 6, n >= 2.at n=17A214601
• Number T(n,k) of standard Young tableaux for partitions of n into distinct parts with largest part k; triangle T(n,k), k>=0, k<=n<=k*(k+1)/2, read by columns.at n=48A219274
• Triangle read by rows: A219274 with rows reversed.at n=57A219356
• Composite squarefree numbers n such that p(i)-5 divides n+5, where p(i) are the prime factors of n.at n=13A225705
• Numbers n such that n^10+10 is prime.at n=35A239347
• Number of 2 X 2 matrices with all elements in {0,...,n} and prime permanent.at n=20A281090
• a(n) = Sum_{k=1..n} k * A088370(n,k).at n=43A309371
• a(n) = a(n-1) + p(n) if p(n) > a(n-1), otherwise a(n) = a(n-1) - p(n), where p is the partition function A000041 (assuming a(n) = 0 for n < 0).at n=36A331165
• Main diagonal of A332363.at n=21A332364
• Number of discrete implications I:L_n^2-> L_n defined on the finite chain L_n={0,1,...n}, which satisfy the identity principle, i.e., I(x,x)=n for all x in L_n.at n=3A367541