20619

Appears in sequences

• a(n) = (2*n-1)*(n^2 -n +6)/6.at n=39A049480
• Numbers k such that sigma(k-phi(k)) = phi(k).at n=12A070170
• Partial sums of A061262.at n=32A176661
• Indices of primes followed by a gap (distance to next larger prime) of 44.at n=18A320720
• Number of strict compositions of n with all adjacent parts (x, y) satisfying x < 2y and y < 2x.at n=55A342341
• For 1<=x<=n, 1<=y<=n, write gcd(x,y) = u*x+v*y with u,v minimal; a(n) = sum of the values of u^2+v^2.at n=26A345434
• Square array A(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where column k is the expansion of e.g.f. B(x)^k, where B(x) is the e.g.f. of A384760.at n=51A384761