26419

Appears in sequences

• Pseudoprimes to base 7.at n=33A005938
• Strong pseudoprimes to base 49.at n=12A020275
• If B is a collection in which there are C(n-1) [Catalan numbers, A000108] things with n points, a(n) is the number of subsets without repetition of B with a total of n points.at n=11A052805
• Numbers n such that 6*10^n + 5*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.at n=21A103038
• a(n) = (2*n^3 + 5*n^2 - 5*n)/2.at n=28A162265
• G.f.: A(x) = exp( Sum_{n>=1} sigma(n)*|A002129(n)|*x^n/n ).at n=16A162420
• The least number s > 1 having exactly n fives in the periodic part of the continued fraction of sqrt(s).at n=17A206585
• Number of (4+1) X (n+1) 0..1 arrays with nondecreasing x(i,j)+x(i,j-1) in the i direction and nondecreasing min(x(i,j),x(i-1,j)) in the j direction.at n=7A250733
• Write n-th prime in binary, then increase each run of 0's by one 0, and increase each run of 1's by one 1. a(n) is the decimal equivalent of the result.at n=41A319406