20685

Appears in sequences

• a(n) = [ 1/(2*t(n+1) - t(n) - t(n+2)) ], where t(n) = tan(Pi/2 - 1/n) satisfies n-1 < t(n) < n for all n >= 1.at n=22A024817
• Numbers having four 3's in base 9.at n=4A043468
• a(n) in base 14 is a repdigit.at n=46A048338
• a(n) = n*(n+1)*(n^2+1)/2.at n=14A071237
• a(n) = n*(n+1)*(2*n^3 - n^2 + 2)/6.at n=9A101383
• Pierce expansion of the cube root of 1/2.at n=11A140076
• Number of n X n binary arrays with all ones connected only in a one by five or five by one block.at n=7A145964
• Number of n X n binary arrays symmetric under horizontal and vertical reflection with all ones connected only in a one by five or five by one block.at n=17A145966
• Triangle, read by rows, that transforms diagonals in the table of coefficients of successive iterations of x*(1+x)^2 (cf. A166888).at n=23A166890
• Column 3 of triangle A166890.at n=4A166893
• Triangle T(n,k) = A008292(n+1,k+1) + A060187(n+1,k+1)- 1 read along rows 0<=k<=n.at n=46A176490
• Triangle T(n,k) read by rows: coefficient [x^k] of the polynomial sum_{k=0..infinity} (2*k+1)^n*binomial(x,k) / 2^x.at n=61A176668
• Number of (n+3)X10 binary arrays with every 4X4 subblock commuting with each horizontal and vertical neighbor 4X4 subblock.at n=10A188103
• Records in A087669.at n=34A192230
• Number of ways 2 domicules can be placed on an n X n square.at n=8A243464