25400

Appears in sequences

• Numbers n such that 2*n*k(n) is rational but not an integer, where k(n) is sum of successive remainders when computing the Euclidean algorithm for (1, 1/sqrt(n)) as defined in A086378 (MuPAD program is given there); numbers belonging to A086378 but not to A088900.at n=17A087414
• Numbers k such that phi(phi(k)) = sigma(rad(k)).at n=32A173748
• Triangle read by rows: number of set partitions of n elements with k circular connectors.at n=58A185983
• Number of nX5 0..2 arrays with no element unequal to a strict majority of its king-move neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards.at n=7A279899
• a(0) = 1; a(n) = Sum_{k=1..n} (-1)^(k+1)*sigma_2(k+1)*a(n-k), where sigma_2() is the sum of squares of divisors (A001157).at n=8A307242
• Number of n element multisets of the 10th roots of unity with zero sum.at n=43A321416
• Number of achiral polyomino rings of length 4n with fourfold rotational symmetry.at n=27A324409
• Number of achiral polyomino rings of length 4n with fourfold rotational symmetry.at n=28A324409
• E.g.f. satisfies A(x) = (1 + x)^(2 * A(x)).at n=5A355780