21104

Appears in sequences

• Number of Costas arrays of order n, counting rotations and flips as distinct.at n=15A008404
• Interprimes which are of the form s*prime, s=16.at n=19A075291
• Number of permutations of 1..n with all differences of elements separated by distances 1 through 7 being respectively unique.at n=15A170813
• Number of permutations of 1..n with all differences of elements separated by distances 1 through 8 being respectively unique.at n=15A170814
• Number of permutations of 1..n with all differences of elements separated by distances 1 through 9 being respectively unique.at n=15A170815
• Expansion of e.g.f. (1 + x + x^2)^x.at n=8A191422
• Irregular triangular array read by rows. T(n,k) is the number of weakly connected relations on n labeled nodes with k arcs. (n>=0, 0<=k<=n^2).at n=40A217563
• Numbers equal to the arithmetic derivative of their Euler totient function.at n=42A248815
• E.g.f.: Product_{k>0} (1 + tanh(x^k/k)).at n=8A270598
• Numbers k such that (83*10^k - 29) / 9 is prime.at n=23A278418