21210

Appears in sequences

• A variant of the recurrence for A001190.at n=21A038751
• Numbers with exactly 5 distinct prime factors each of which is a palindrome.at n=1A046403
• Factorial expansions of the entries in A085219.at n=47A085221
• Numbers n which are a proper multiple (>1) of A068505(n) (= n read in base m+1 where m = largest digit of n).at n=34A089584
• Binary numbers with 2 replacing 1 in odd positions.at n=30A095914
• A Chebyshev transform of the first kind of the Catalan numbers.at n=11A102880
• Number of base 10 circular n-digit numbers with adjacent digits differing by 4 or less.at n=5A125347
• Take the base-3 representation of n, render that in decimal notation and take the base-3 representation of n again.at n=21A126135
• a(n) = sum of all divisors of all numbers k such that n^2 <= k < (n+1)^2.at n=17A168012
• Number of (n+3) X 7 binary arrays with every 4 X 4 subblock commuting with each horizontal and vertical neighbor 4 X 4 subblock.at n=13A188100
• Indices of consecutive maxima in A214123.at n=17A214124
• Number of digits in the decimal expansion of the number of partitions of 6^n.at n=11A248733
• Check the abundance of a number and iterate the test replacing at every step the sum of the divisors of the previous number. Sequence lists the least numbers whose abundances last n steps.at n=14A286659
• Numbers k that are multiples of the digital sum of k-1, k and k+1.at n=31A303068
• Sum of sums of omegas of parts over all integer partitions of n.at n=27A325536
• The number of overpartitions of n whose Frobenius symbols have only odd parts in the top row.at n=39A347206
• Number of integer partitions of n > 0 that are not the first sums of any composition with all parts > 1.at n=36A391620