21656

Appears in sequences

• a(1) = 5; a(n+1) = a(n)-th nonprime, where nonprimes begin at 4.at n=38A025010
• Number of ways of covering a 2n X 2n lattice with 2n^2 dominoes of which exactly 6 are horizontal (or vertical) dominoes.at n=2A054344
• Number of idempotent 3 X 3 -n..n matrices.at n=8A223455
• If n^2 has an even number of digits, write n after the left half of the digits of n^2 and before the right half, otherwise if n^2 has 2t+1 digits, write n after the first t digits of n^2 and before the last t+1 digits.at n=15A274620