23884

Appears in sequences

• a(n) = s(1)s(n) + s(2)s(n-1) + ... + s(k)s(n-k+1), where k = [ n/2 ], s = (F(2), F(3), F(4), ...).at n=15A025105
• Number of unlabeled 7-ary cacti having n polygons.at n=6A054369
• Start with any initial string of n numbers s(1), ..., s(n), with s(1) = 2, other s(i)'s = 2 or 3 (so there are 2^(n-1) starting strings). The rule for extending the string is this as follows: To get s(n+1), write the string s(1)s(2)...s(n) as xy^k for words x and y (where y has positive length) and k is maximized, i.e., k = the maximal number of repeating blocks at the end of the sequence. Then a(n) = number of starting strings for which k > 1.at n=15A093370
• Lower triangular matrix T, read by rows, that shifts left one column under the matrix square of T, with T(n,0)=T(n,1) for n>0 and T(n,n)=1 for n>=0.at n=30A098539
• Column 2 of triangle A098539, which shifts left one column under the matrix square.at n=5A098541
• a(n) = A121880(2*n)/2.at n=7A211973
• Number n such that the sum of its proper evil divisors (A001969) equals n.at n=35A230587
• Number of nX4 0..3 arrays x(i,j) with each element horizontally or vertically 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=5A230895
• Number of nX6 0..3 arrays x(i,j) with each element horizontally or vertically 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=3A230897
• T(n,k)=Number of nXk 0..3 arrays x(i,j) with each element horizontally or vertically 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=39A230899
• T(n,k)=Number of nXk 0..3 arrays x(i,j) with each element horizontally or vertically 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=41A230899
• Number of partitions of n, where the difference between the number of odd parts and the number of even parts is 7.at n=49A240016
• Expansion of (-1 + Product_{k>=1} 1 / (1 + (-x)^k))^4.at n=28A341243