21892

Appears in sequences

• Number of binary vectors of length n containing no singletons.at n=22A006355
• Number of distinct permutations generated by shuffling n cards with "clump size" <= 2.at n=18A047992
• Expansion of 2*x*(1 - x)/(1 - 3*x + x^2).at n=11A052995
• Layer counting sequence for hyperbolic tessellation by cuspidal triangles of angles (Pi/3,Pi/3,0) (this is the classical modular tessellation).at n=19A054886
• a(0) = 1, then twice the Fibonacci sequence.at n=21A055389
• Row sums of array T in A055818; twice the odd-indexed Fibonacci numbers after initial term.at n=11A055819
• a(n) = round(sqrt(a(n-2)^2 + a(n-1)^2)) with a(0) = 1 and a(1) = 2.at n=40A063827
• Numbers k such that the period of the continued fraction for sqrt(5)*k is 2.at n=36A065030
• Number of ways to tile a 3 X 2n room with 1 X 2 Tatami mats. At most 3 Tatami mats may meet at a point.at n=19A068922
• Polynomial (1/3)*n^3 + (9/2)*n^2 + (85/6)*n - 2.at n=36A073775
• Numbers with two representations as the sum of two Fibonacci numbers.at n=18A078642
• Number of meaningful differential operations of the n-th order on the space R^6.at n=17A090991
• Expansion of (1+x)^2/(1-x^2-x^4).at n=41A096748
• "Rounded hypotenuses": a(n) = round(sqrt(a(n-1)^2 + a(n-2)^2)), a(1)=1, a(2)=3.at n=39A104804
• a(n) = 2*F(n-1) = L(n) - F(n), where F(n) and L(n) are Fibonacci and Lucas numbers respectively.at n=22A118658
• Number of base 4 n-digit numbers with adjacent digits differing by one or less.at n=10A126358
• Expansion of g.f. x*(1+x+x^2)/(1-x-x^2).at n=20A128588
• Row sums of triangle A131779.at n=19A131780
• a(0)=0; a(1)=1; a(n) = Sum_{k=1..floor(n^(1/3))} a(n-k) for n >= 2.at n=27A132916
• Expansion of x - x^2*(2*x+1)*(x^2-2) / ( (x^2-x-1)*(x^2+x-1) ).at n=20A133585