21078

Appears in sequences

• a(n) = s(1)s(n) + s(2)s(n-1) + ... + s(k)s(n+1-k), where k = [ (n+1)/2 ], s = A000201 (lower Wythoff sequence).at n=44A024685
• Interprimes which are of the form s*prime, s=18.at n=37A075293
• Number of base 20 circular n-digit numbers with adjacent digits differing by 6 or less.at n=4A125408
• Partial sums of A174928.at n=35A174929
• p-INVERT of (1,0,0,0,1,0,0,0,0,0,...), where p(S) = (1 - S)^2.at n=27A292325
• Number of nX5 0..1 arrays with every element unequal to 0, 1, 3 or 4 king-move adjacent elements, with upper left element zero.at n=12A303805
• a(n) = [x^(n^2)] Product_{k=1..n} Sum_{m>=0} x^(k*m^2).at n=11A321139
• Squares where knight moving to a lowest unvisited square on a spirally numbered board will have no available moves.at n=14A323714
• Positive integers k having no duplicated digit such that concatenating all successive absolute differences between two successive digits of k produces a divisor of k.at n=89A338641
• Number of regions formed in a hexagon by straight line segments when connecting the n-1 points between each corner that divide each edge into n equal parts to the n-1 points on the edge on the opposite side of the hexagon.at n=9A367662