70561

Appears in sequences

• Strong pseudoprimes to base 26.at n=21A020252
• Strong pseudoprimes to base 48.at n=28A020274
• Number of pairs with two different elements which can be obtained by selecting unique elements from two sets with n+1 and n^2 elements respectively and n common elements.at n=41A085490
• Triangle, read by rows, T(n, k) = T(n, k-1) + (k+1)*n!, T(n, 0) = 1.at n=32A105064
• a(n) = 1 + 2*n*n!.at n=7A155159
• G.f.: exp( Sum_{n>=1} A001333(n)^2 * x^n/n ) where A001333(n) = A002203(n)/2, one-half the companion Pell numbers.at n=8A204061
• Numbers n such that (n(n+1)/2) modulo sigma(n) = n.at n=17A232538
• Number of non-congruent solutions of x^2 + y^2 + z^2 + t^2 == 0 mod n.at n=40A240547
• Number of non-congruent solutions of x^2+y^2 == z^2+w^2 (mod n).at n=40A316148
• Number of compositions (ordered partitions) of n into distinct squarefree parts.at n=43A331846
• Distance from 10^n to the next prime triplet.at n=26A357052
• Let q be the n-th prime power (A246655), then a(n) = q^3 + q^2 - q; number of solutions to x*y = z*w in the finite field F_q.at n=19A367014
• a(n) = Sum_{1 <= x_1, x_2 <= n} sigma( n/gcd(x_1, x_2, n) ).at n=40A373129
• Least k such that A056100(k) = n or -1 if no such k exists.at n=41A386871