21208

Appears in sequences

• Denominators of continued fraction convergents to sqrt(30).at n=7A041049
• Denominators of continued fraction convergents to sqrt(270).at n=7A041507
• Denominators of continued fraction convergents to sqrt(750).at n=13A042445
• Expansion of (1-x)/(1-2*x-2*x^2-2*x^3).at n=10A077843
• Duplicate of A077843.at n=10A077994
• G.f. A(x) satisfies A(x) = 1/Product_{k>0} (1-x^k*A(x)).at n=9A145268
• Number of -3..3 arrays x(0..n-1) of n elements with zero sum, and adjacent elements not equal modulo three (with -1 modulo 3 = 2).at n=7A199904
• T(n,k)=Number of -k..k arrays x(0..n-1) of n elements with zero sum, and adjacent elements not equal modulo three (with -1 modulo 3 = 2).at n=52A199909
• Number of primes of the form (x+1)^11 - x^11 having n digits.at n=58A221984
• Numbers k such that Sum_{j=1..k} (sigma(j) + phi(j) + tau(j)) == 0 (mod k).at n=7A227008
• Positive integers m such that pi(m^3) = pi(j^3) + pi(k^3) for some 0 < j <= k < m.at n=24A262409
• Number of pairs of functions (f,g) on [n] such that fg is an idempotent.at n=4A275025