31131

Appears in sequences

• Number of distinct values taken by 4^4^...^4 (with n 4's and parentheses inserted in all possible ways).at n=13A003019
• Numbers with multiplicative digital root value 9.at n=31A034056
• Numbers with at least 2 distinct digits and whose "rotations" (including the number itself) are multiples of these digits; repeated digits allowed but digit 0 not allowed.at n=25A066484
• Decimal encoding of the prime factorization of n: concatenation of prime factors and exponents.at n=37A067599
• a(1) = 11 by convention; for n > 1, if n = p^a*q^b... then a(n) = concatenate(p,a,q,b,...).at n=38A068633
• Concatenations of pairs of primes that differ by 100.at n=3A103523
• Numbers k such that k and k^2 use only the digits 0, 1, 3, 6 and 9.at n=61A136850
• Numbers k such that k and k^2 use only the digits 1, 2, 3, 6 and 9.at n=28A136981
• Numbers k such that k and k^2 use only the digits 1, 3, 4, 6 and 9.at n=24A137027
• Numbers k such that k and k^2 use only the digits 1, 3, 5, 6 and 9.at n=23A137035
• Numbers k such that k and k^2 use only the digits 1, 3, 6, 7 and 9.at n=18A137039
• Numbers k such that k and k^2 use only the digits 1, 3, 6, 8 and 9.at n=17A137041
• Numbers k such that k and k^2 use only the digits 1, 3, 6 and 9.at n=8A137042
• a(1) = 1; thereafter a(n) is always the smallest integer > a(n-1) not leading to a contradiction, such that the concatenation of any three consecutive digits in the sequence is a prime.at n=20A152608
• Composite numbers whose multiplicative digital root is 9.at n=25A201024
• List of primitive words over the alphabet {1,3}.at n=39A213970
• Maximal nonempty {1,3}-chunks of a 4-day-old string in a "Look and Say" sequence.at n=24A244047
• Numbers k such that the product of their digits divides both k and R(k), where R(k) is the digits reverse of k.at n=37A277856
• Numbers that are divisible by the sum of their digits and for which the sum of digits equals the product of digits.at n=20A280355
• 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=45A305257