21439

Appears in sequences

• Number of Van Lier sequences of length n.at n=6A005272
• Crystal ball sequence for diamond.at n=29A007904
• Composite numbers n such that sigma(n+24) = sigma(n) + 24.at n=20A054983
• Numbers k that are the products of two distinct primes such that 2*k-1, 4*k-3, 8*k-7, 16*k-15 and 32*k-31 are also products of two distinct primes.at n=29A177214
• Numbers k that are the products of two distinct primes such that 2*k-1, 4*k-3, 8*k-7, 16*k-15, 32*k-31 and 64*k-63 are also products of two distinct primes.at n=11A177215
• Numbers n such that n contains exactly 5 digits, all distinct, and n^2 contains exactly 9 distinct digits.at n=17A204691
• a(n) = 4*n^3 - 18*n^2 + 27*n - 12.at n=18A271828
• Numbers k such that k and 4k, taken together, contain all digits 1 though 9 at least once.at n=39A346135
• Number of minors in the n-sunlet graph.at n=8A354671
• a(n) = coefficient of x^n in A(x) such that x = Sum_{n=-oo..+oo} x^n * (1 - x^n/A(-x))^n.at n=10A360233
• G.f. A(x) satisfies x = Product_{n>=1} (1 - x^n*A(x)) * (1 - x^(n-1)/A(x)) * (1 + x^n).at n=10A384269