19230

Appears in sequences

• Becomes prime after n iterations of f(x) = sigma(x)-1 (least inverse of A039655).at n=22A039656
• Numbers k such that sigma(k)+1 is a square and sets a new record for such squares.at n=35A063729
• Take pairs (a, b), sorted on a, such that T(a)+T(b)=concatenation of a and b, where T(k) is the k-th triangular number A000217(k). Sequence gives values of a.at n=30A096031
• Sequence defined by the recurrence formula a(n+1)=sum(a(p)*a(n-p)+k,p=0..n)+l for n>=1, with here a(0)=1, a(1)=9, k=0 and l=-2.at n=6A177171
• Number of 5-divided binary words of length n.at n=15A210322
• Number of ordered triples (w,x,y) with all terms in {1,...,n} and w^3 < x^3 + y^3.at n=30A211650
• Numbers n such that A002088(n) < 3n^2/Pi^2.at n=35A285022
• Number of T_0 set-systems covering n vertices that are closed under intersection.at n=5A309615
• Number of n element multisets of the 15th roots of unity with zero sum.at n=47A321418
• G.f.: Sum_{k>=0} x^(k^2) * Product_{j=1..k} 1/(1 - x^j)^4.at n=18A376712