-3421

Appears in sequences

• Expansion of (1-x)^(-1)/(1+x^2+2*x^3).at n=28A077890
• a(n) = M(2^n), where M(n) is Mertens's function, A002321.at n=34A084236
• Alternating sum of hexagonal pyramidal numbers.at n=21A266677