42583

Appears in sequences

• a(n) = |Sum_{k=0..n} (-1)^k*(2k)!!|.at n=6A290044
• Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-1) - b(n-2) + 1, where a(0) = 1, a(1) = 2, b(0) = 3, and (a(n)) and (b(n)) are increasing complementary sequences.at n=20A294562
• a(n) = Sum_{k=1..n} sigma_2(k) * floor(n/k).at n=43A356042