211297

Properties

Appears in sequences

• Number of triangular polyominoes (or triangular polyforms, or polyiamonds) with n cells (turning over is allowed, holes are allowed, must be connected along edges).at n=15A000577
• Numerators of Taylor series expansion of (exp(1-exp(x))-1)/(1-exp(x)).at n=15A051780
• Number of (n+3) X 9 0..1 matrices with each 4 X 4 subblock idempotent.at n=22A224566
• Expansion of Sum_{i>=1} mu(i)^2*x^i/(1 - x^i) / Product_{j>=1} (1 - x^j), where mu() is the Moebius function (A008683).at n=36A281573
• a(n) is the least number k such that there are exactly n biquadratefree powerful numbers (A338325) between k^2 and (k+1)^2.at n=6A338327
• Prime numbersat n=18919