22121

Appears in sequences

• Number of n-node trees with a forbidden limb of length 3.at n=17A002989
• a(n) = C(n+2,3) + C(n,3) + C(n-1,3).at n=35A006004
• Strong pseudoprimes to base 63.at n=20A020289
• Numbers whose product of decimal digits equals its sum of binary digits.at n=32A064003
• Left-to-right binary enumeration.at n=41A081242
• Pascal-(1,7,1) array.at n=58A081582
• Pascal-(1,7,1) array.at n=62A081582
• Structured disdyakis triacontahedral numbers (vertex structure 7).at n=10A100159
• n expressed in Fibonacci binary-like number system using only 1's and 2's.at n=16A108960
• a(n) = Sum_{k=1..n} k*sigma(k).at n=33A143128
• Number of nondecreasing arrangements of 6 numbers in -(n+4)..(n+4) with sum zero and not more than two numbers equal.at n=9A188239
• List of primitive words over the alphabet {1,2}.at n=47A213969
• List of subwords (or factors) of the Thue-Morse "1,2"-word A001285.at n=33A214215
• Numbers whose largest digit of all divisors is 2.at n=29A221697
• Composite numbers n such that largest digit of all divisors of n is 2.at n=8A221698
• Shortest (x+1,2x)-code of n.at n=10A233135
• The number of P-positions in the game of Nim with up to 4 piles, allowing for piles of zero, such that the number of objects in each pile does not exceed n.at n=28A241522
• Numbers n for which the numbers 6n+1, 3n+2, 6n+7 are all odd composite squarefree numbers, but none are semiprimes.at n=37A263510
• Semiprimes such that sum of digits equals product of digits.at n=16A272436
• If pd(x) is the product of the digits of the number x and sd(x) the sum of the digits of the number x then the sequence lists all the positive numbers n for which pd(n) = sd(n) and sd(pd(n)) = pd(sd(n)).at n=42A305257