21267

Appears in sequences

• Number of n-stacks with strictly receding walls, or the number of Type A partitions of n in the sense of Auluck (1951).at n=41A001522
• Larger members of g-reduced amicable pairs a < b such that sigma(a) = sigma(b) = a + b + gcd(a,b).at n=40A054572
• This table shows the coefficients of combinatorial formulas needed for generating the sequential sums of p-th powers of binomial coefficients C(n,6). The p-th row (p>=1) contains a(i,p) for i=1 to 6*p-5, where a(i,p) satisfies Sum_{i=1..n} C(i+5,6)^p = 7 * C(n+6,7) * Sum_{i=1..6*p-5} a(i,p) * C(n-1,i-1)/(i+6).at n=23A087110
• a(1)=1, a(2)=2. a(n) is the a(n-1)th integer from among those positive integers coprime to a(n-2).at n=25A126881
• a(n) = 2*a(n-1) - a(n-2) - a(n-4).at n=30A131041
• Total number of restricted right truncatable primes in base n.at n=34A133757
• Number of 6Xn -1,1 arrays such that the sum over i=1..6,j=1..n of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute n-across galley oarsmen left-right at 6 fore-aft positions so that there are no turning moments on the ship).at n=17A225346
• Numbers x such that the sum of all their cyclic permutations is equal to that of all cyclic permutations of sigma(x) and all cyclic permutations of Euler totient function phi(x).at n=20A247317
• Expansion of the series reversion of Sum_{k>=1} x^(k*(k+1)/2).at n=15A291418
• Least k > 1 such that all divisors d of (k^(2n+1)+1)/(k+1) satisfy d == 1 (mod 2n+1).at n=31A298310
• Dirichlet g.f.: Product_{k>=2} 1 / (1 - k^(-s))^(k^2).at n=47A329125
• Number of fixed-point free involutions in a fixed Sylow 2-subgroup of the symmetric group of degree 2n.at n=14A332840
• Number of fixed-point free involutions in a fixed Sylow 2-subgroup of the symmetric group of degree 2n.at n=15A332840
• Number of fixed-point free involutions in a fixed Sylow 2-subgroup of the symmetric group of degree 4n.at n=7A332869
• a(n) = A333552(A333551(n)): indices of terms in Recamán's sequence A005132 where the construction avoided a record-sized collision.at n=44A333553
• Number of subsets of {2..n} such that the product of the elements is a decimal palindrome.at n=48A339508
• Numbers that are the sum of seven fourth powers in six or more ways.at n=27A345572
• Numbers that are the sum of seven fourth powers in seven or more ways.at n=6A345573
• Numbers that are the sum of seven fourth powers in eight or more ways.at n=2A345574
• Numbers that are the sum of seven fourth powers in nine or more ways.at n=1A345575