21581

Appears in sequences

• G.f.: Product_{k>=1} (1 + x^(2*k - 1)) / (1 - x^(2*k)).at n=50A006950
• a(n) = n*(7*n^2-4)/3.at n=21A063521
• Number of n X 4 binary arrays with each 1 adjacent to exactly one 1 vertically and one 1 horizontally.at n=14A183336
• Bisection of A006950 (the even part).at n=25A233758
• 5th power analog of Keith numbers.at n=17A281916
• a(n) = Sum_{k=1..n} k^2*tau_3(k), where tau_3 is A007425.at n=18A319088