27089

Appears in sequences

• Numbers k such that sigma(k) divides sigma(k+1), where sigma(k) is sum of positive divisors of k.at n=26A058072
• Numbers k such that sigma(k+1) = 3 * sigma(k).at n=4A077087
• Numbers k such that sigma_odd(k) = sigma_odd(k+1), where sigma_odd(k) is the sum of the odd divisors of k (A000593).at n=1A164522
• G.f.: 1/(1 - x/(1 - x^3/(1 - x^6/(1 - x^10/(1 - x^15/(1 - x^21/(1 -...- x^(n*(n+1)/2)/(1 -...))))))), a continued fraction.at n=28A206740
• Numbers k such that sigma(triangular(k)) = sigma(k)^2.at n=9A232355
• Numbers k with the property that it is possible to write the base 2 expansion of k as concat(a_2,b_2), with a_2>0 and b_2>0 such that, converting a_2 and b_2 to base 10 as a and b, we have sigma(a + b) = sigma(k).at n=16A258843
• Numbers k such that A113184(k) = A113184(k+1).at n=18A348585