31311

Appears in sequences

• Number of homeomorphically irreducible (or series-reduced) trees with n pendant nodes, or continua with n non-cut points, or leaves.at n=15A007827
• a(n) = floor((3rd elementary symmetric function of 2,3,...,n+3)/(2+3+...+n+3)).at n=26A024178
• Numbers with multiplicative digital root value 9.at n=32A034056
• a(n) = (2*n-1)*(n^2 -n +2)/2.at n=31A063488
• 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=26A066484
• Smallest a(n) > a(n-1) such that a(n)^2+a(n-1)^2 is a perfect square, with a(1)=5.at n=29A076671
• Smallest a(n)>a(n-1) such that a(n)^2+a(n-1)^2 is a perfect square, a(1)=9.at n=29A076674
• Apparently an erroneous version of A007827.at n=12A129859
• Number of n X n binary arrays symmetric under 90 degree rotation with all ones connected only in a 1010-1111-0101 pattern in any orientation.at n=16A147434
• Totally multiplicative sequence with a(p) = 10p+1 for prime p.at n=27A166668
• Composite numbers whose multiplicative digital root is 9.at n=26A201024
• E.g.f. satisfies 2*A(x)-exp(A(x))+1=sin(x).at n=6A207326
• List of primitive words over the alphabet {1,3}.at n=41A213970
• Numbers divisible by both the sum of the squares of their digits and the product of their digits.at n=9A244857
• a(n) = n^2*(7*n - 5)/2.at n=21A262000
• 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=38A277856
• Numbers that are divisible by the sum of their digits and for which the sum of digits equals the product of digits.at n=21A280355
• Numbers m such that there are precisely 19 groups of order m.at n=15A298910
• 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=46A305257
• Numbers k such that k-1, k and k+1 are all composite with four, five and six (not necessarily distinct) prime factors respectively.at n=4A342246