23648

Appears in sequences

• Number of sets S = {a_1, a_2, ..., a_k}, with 1 < a_i < a_j <= n such that no a_j divides the product of all the others.at n=24A023995
• a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (Lucas numbers), t = (odd natural numbers).at n=23A024473
• a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (Lucas numbers), t = (odd natural numbers).at n=22A025093
• First partial sums of A005409; second partial sums of A001333.at n=10A048777
• a(n) = n * prime(prime(n)).at n=31A080697
• Numbers n such that n, n+1, n+2, n+3, n+4 are all of the form x^2+2*y^2 for nonnegative x, y.at n=15A096783
• Numbers n such that 6*10^n + R_n + 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.at n=8A103029
• Number of permutations of length n which avoid the patterns 2341, 3421, 4123.at n=9A116822
• Numbers n such that phi(n) = phi(n+7), with Euler's totient function phi = A000010.at n=24A179189
• Number of (n+2) X 7 binary arrays with each 3 X 3 subblock having rows and columns in lexicographically nondecreasing order.at n=7A184544
• Number of (n+2) X 10 binary arrays with each 3 X 3 subblock having rows and columns in lexicographically nondecreasing order.at n=4A184547
• E.g.f. satisfies: A(x) = x + arcsinh(A(x))^2.at n=5A185190
• Number of length n+3 0..7 arrays with every four consecutive terms having the sum of some three elements equal to three times the fourth.at n=10A248536
• Expansion of Product_{k>=1} ((1 + x^k) / (1 - x^(3*k)))^k.at n=19A285446
• Number of unlabeled nonempty hypertrees with up to n vertices and no singleton edges.at n=12A304937
• Numbers k such that the coefficient of x^k in the expansion of Product_{m >= 1} (1-x^m)^15 is zero.at n=10A322043
• Expansion of 1 / (chi(-x) * chi(-x^3)) in powers of x where chi() is a Ramanujan theta function.at n=51A328798