21004
domain: N
Appears in sequences
- Number of asymmetric n-celled polyominoes with 1 hole.at n=12A057426
- Numbers n such that sigma(n+1)+sigma(n)=3n.at n=6A067806
- Numbers k such that (sigma(k)+sigma(k+1))/k is an integer.at n=7A068078
- 5-Smith numbers.at n=5A103126
- Expansion of x*(1-x)/(1-x+2*x^3-x^4).at n=44A104554
- Eight bishops and one elephant on a 3 X 3 chessboard. G.f.: (1+x-5*x^2)/(1-3*x-x^2+6*x^3).at n=11A175655
- a(n) is the smallest number k such that d(1)*1! + d(2)*2! + ... + d(p)*p! = n^2, where d(i) are the decimal digits of k.at n=21A198095
- Number of nX4 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 1 0 and 1 1 1 vertically.at n=8A207875
- Expansion of Product_{k>=1} 1/(1 + x^k)^(k*(2*k-1)).at n=14A295121
- Self-convolution of the Dedekind psi function (A001615).at n=37A307502
- Number of chordless cycles in the n X n queen graph.at n=5A361184
- Numbers k such that 16 * 3^k + 1 is prime.at n=26A387060