21020

Appears in sequences

• Each permutation in the list A060117 converted to Site Swap notation, with digits reversed. "Zero throws" (fixed elements) indicated with 0's.at n=36A060496
• Numbers k such that k-1, k-3, k-7 and k-9 are all prime.at n=19A064974
• 1 + n-th prime is harmonic.at n=7A074692
• Numbers k such that the square of k contains sigma(k) as a substring, in base 10.at n=12A113654
• Numbers encoded in an alternate, sometimes more compact, binary system with a third, dual-purpose, prefix/delimiter symbol not always required.at n=6A140116
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (-1, 0, 0), (0, 1, 0), (1, -1, -1), (1, -1, 0)}.at n=11A148125
• a(n) = 1000*n + 20.at n=20A157510
• a(n) = 25*n^2 - 5.at n=28A158446
• Smallest k such that tau(k)=reversal(k-n).at n=19A241474
• Number T(n,k) of rooted identity trees with n nodes and colored non-root nodes using exactly k colors; triangle T(n,k), n>=1, 0<=k<=n-1, read by rows.at n=38A256068
• Union of all unique coefficients of all powers of the g.f. A(x) of this sequence, starting with A(0)=2 and A'(0)=3.at n=70A262975
• Number of length n arrays of permutations of 0..n-1 with each element moved by -4 to 4 places and exactly one more element moved upwards than downwards.at n=9A263760
• Numbers n such that there are precisely 15 groups of orders n and n + 1.at n=9A295995
• Number of length n self-avoiding walks on the kisrhombille tiling starting at a degree 4 vertex.at n=6A326745