253952

Appears in sequences

• arctan(tanh(x)*tan(x))=2/2!*x^2-128/6!*x^6+253952/10!*x^10...at n=2A012670
• Expansion of (1 + x - 2*x^2)/(1 - 2*x)^2.at n=14A052951
• a(i) = the number of occurrences of 9's in the palindromic compositions of n=2*i-1 = the number of occurrences of 10's in the palindromic compositions of n=2*i.at n=13A079862
• Number of tilings of a 7 X n rectangle using right trominoes and 2 X 2 tiles.at n=9A219948
• Number of tilings of a 9 X n rectangle using right trominoes and 2 X 2 tiles.at n=7A219950
• Multiply a(n-1) by 2 and drop all 0's.at n=21A242350
• a(1) = 1, a(2) = 2, a(3) = 5, a(4) = 8 and a(5) = 15, a(n) = Sum_{j=1..n-1} a(j).at n=18A257548