661598

Appears in sequences

• Number of nX5 0..3 arrays x(i,j) with each element horizontally, vertically or antidiagonally next to at least one element with value (x(i,j)+1) mod 4 and at least one element with value (x(i,j)-1) mod 4, no adjacent elements equal, and upper left element zero.at n=8A230828
• a(n) = Sum_{k=1..n} k^2*sigma_2(k), where sigma_2 is A001157.at n=18A364268