20214

Appears in sequences

• Generalized Catalan Numbers x^3*A(x)^2 -(1-x+x^3+x^4)*A(x) + 1 =0.at n=20A023433
• Values of e, the lesser key or generating number for Pythagorean triangles in which S (the odd short leg) and U (the hypotenuse) are twin primes.at n=41A051892
• Numbers n such that [A070080(n), A070081(n), A070082(n)] is an obtuse isosceles integer triangle with prime side lengths.at n=26A070135
• a(n) = 729*n - 198.at n=27A156772
• Numbers n such that n+(n+1), n^2+(n+1)^2, n+(n+1)^2, n^2+(n+1) are all prime.at n=26A216270
• Number of nX5 0..2 arrays with diagonals and rows unimodal and antidiagonals nondecreasing.at n=2A224307
• T(n,k)=Number of nXk 0..2 arrays with diagonals and rows unimodal and antidiagonals nondecreasing.at n=23A224310
• Number of 3Xn 0..2 arrays with diagonals and rows unimodal and antidiagonals nondecreasing.at n=4A224311
• Numbers k such that if x = k - phi(k) then k = sigma(x) - x, where phi(k) is the Euler totient function.at n=13A239802
• The 300-degree spoke (or ray) of a hexagonal spiral of Ulam.at n=41A244804
• Maximum starting value of X such that repeated replacement of X with X-ceiling(X/5) requires n steps to reach 0.at n=40A279075
• a(n) = Sum_{-n<i<n, -n<j<n, gcd{i,j}=3} (n-|i|)*(n-|j|)/4.at n=32A331775
• Number of integer partitions of n whose length (number of parts) is equal to the sum of some submultiset.at n=37A367212
• Irregular triangle read by rows: T(n,k) is the number of flattened Catalan words of length n with exactly k symmetric peaks, with k >= 0.at n=45A372883