20953

Appears in sequences

• Denominators of continued fraction convergents to sqrt(766).at n=11A042477
• a(n) = 2*prime(n)^2 - prime(n+1)^2.at n=35A064051
• Sum of squares of digits of n is equal to the largest prime factor of n reversed, where the largest prime factor is not a palindrome.at n=31A074303
• Semiprimes in A033951.at n=22A113691
• Multiples of 23 whose digit reversal + 1 is also a multiple of 23.at n=37A166393
• Number of (n+2) X 7 binary arrays with every 3 X 3 subblock commuting with each horizontal and vertical neighbor 3 X 3 subblock.at n=16A190029
• Number of n X 3 0..1 arrays avoiding 0 0 0 horizontally and 0 0 1 vertically.at n=5A207083
• T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 horizontally and 0 0 1 vertically.at n=33A207088
• Number of 6Xn 0..1 arrays avoiding 0 0 0 horizontally and 0 0 1 vertically.at n=2A207092
• Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-1)*b(n-2), where a(0) = 1, a(1) = 3, a[2] = 5, b(0) = 2, b(1) = 4, and (a(n)) and (b(n)) are increasing complementary sequences.at n=14A295364
• Numbers k such that phi(k) > phi(k+1) > phi(k+2) > phi(k+3) where phi is the Euler totient function (A000010).at n=35A326817
• a(n) = Sum_{k=0..n} sigma(k^2 + 1), where sigma(k) is the sum of divisors of k (A000203).at n=35A333172