21196

Appears in sequences

• Numbers n such that n through n+5 have the same number of distinct prime factors.at n=25A045934
• Intrinsic 10-palindromes: n is an intrinsic k-palindrome if it is a k-digit palindrome in some base.at n=22A060947
• q-factorial numbers 3!_q.at n=27A069778
• Even pseudoprimes to base 9.at n=26A090083
• Number of -2..2 arrays x(i) of n+1 elements i=1..n+1 with set{t,u,v in 0,1}((x[i+t]+x[j+u]+x[k+v])*(-1)^(t+u+v)) having two, three or four distinct values for every i,j,k<=n.at n=11A211568
• The number of permutations of length n sortable by 3 prefix reversals (in the pancake sorting sense).at n=28A228398
• Pseudoprimes to base 9 that are not squarefree.at n=25A306448
• a(n) = m is the least m = b*c > a(n-1) such that (b+c)*n = m-1 where 1 < b <= c < m.at n=26A364171
• Numbers k such that k and k+2 are both terms in A380846.at n=5A381073