21779

Appears in sequences

• Number of odd primes p < 10^n such that p+2 = product of 2 primes (no twin Chen primes).at n=5A111067
• Numerators of partial sums for a series for Pi/3.at n=5A130413
• a(n) = 20*n^2 - 1.at n=32A158491
• Smallest k>0 such that (5^n-k)*5^n-1 and (5^n-k)*5^n+1 are a twin prime pair or 0 if no such k exists.at n=52A212488
• Partial sums of A246031.at n=16A255364
• (1/8) * number of ways to select 3 distinct points forming a triangle of unsigned area = 1 from a square of grid points with side length n.at n=19A320544
• Expansion of Product_{1 <= i < j} (1 + x^(i*j)).at n=52A321286
• Expansion of g^2/(1 - x^3*g^2), where g = 1+x*g^3 is the g.f. of A001764.at n=7A391124