19378

Appears in sequences

• a(n) = Sum_{k=0..2*n-3} T(n, k)*T(n, k+3), T given by A027960.at n=4A027987
• a(n) = a(1) + a(2) + ... + a(n-1) - a(m) for n >= 4, where m = 2^(p+1) + 2 - n and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = 1, a(2) = 3, and a(3) = 1.at n=16A049917
• a(n) is the number of divisors of n-th even perfect number.at n=20A061645
• Numbers m such that (1+i)^m - i is a Gaussian prime.at n=25A103329
• Indices n such that the 3 X 3 matrix with components (row by row) prime(n+k), 0 <= k <= 8, has zero determinant.at n=27A117345
• Indices n == 1 (mod 9) such that the 3 X 3 matrix with components (row by row) prime(n+k), 0 <= k <= 8, has zero determinant.at n=3A117359
• Triangle, read by rows, equal to the matrix cube of triangle A185620.at n=29A185628
• Column 1 of triangle A185628.at n=6A185630
• G.f.: exp( Sum_{n>=1} (x^n/n) * Product_{d|n} (1 + d*x^n) ).at n=41A205478
• Number of length n inversion sequences avoiding the patterns 100, 102, and 201.at n=9A279562
• Numbers k for which R(k) + 3*10^floor(k/2) is prime, where R(k) = (10^k-1)/9 (repunit: A002275).at n=13A331866
• a(n) = (a(n-1) + a(n-3))/2^m, where 2^m is the highest power of 2 that divides both a(n-1) and a(n-3), with a(0) = a(1) = a(2) = 1.at n=46A341313