23448

Appears in sequences

• Number of irreducible polynomials (over the rationals) of form a*x^2+b*x+c, 1 <= a,b,c <= n.at n=28A079671
• Consider the mapping f(a/b) = (a^2 +b^2)/(a+b). Taking a =1, b = 2 to start with and carrying out this mapping repeatedly on each new (reduced) rational number gives the following sequence 1/2,5/3,17/4,305/21,... Sequence contains the denominators.at n=5A081480
• Number of 11-almost primes less than or equal to 10^n.at n=7A120052
• Number of 4-element subsets that can be chosen from {1,2,...,4*n} having element sum 8*n+2.at n=24A204468
• Expansion of Product_{k>=0} 1/(1-x^(4*k+1))^3.at n=32A261632
• Number of nXnXn triangular 0..6 arrays with some element plus some adjacent element totalling 6+1 or 6-1 exactly once.at n=2A270604
• T(n,k)=Number of nXnXn triangular 0..k arrays with some element plus some adjacent element totalling k+1 or k-1 exactly once.at n=30A270606
• Number of 3X3X3 triangular 0..n arrays with some element plus some adjacent element totalling n+1 or n-1 exactly once.at n=5A270608
• Row sums of A285116: a(n) = 2 + Sum_{k=1..(n-1)} (C(n-1,k-1) bitwise-or C(n-1,k)), a(0) = 1, a(1) = 2.at n=15A285113
• a(0)=1; a(1)=1; for n >= 2, a(n) = a(n-A000120(n)) + a(n-1-A023416(n)).at n=38A297216
• Decimal representation of binary numbers with string structure 10s00, s in {0,1}*, such that it results in a non-palindromic cycle of length 4 in the Reverse and Add! procedure in base 2.at n=21A306514