21523361

Properties

Appears in sequences

• Largest prime factor of 9^n + 1.at n=8A002592
• a(n) = (3^n + 1)/2.at n=16A007051
• a(n) = 2*a(n-1) + 3*a(n-2), a(0) = a(1) = 1.at n=16A046717
• Number of periodic palindromic structures of length n using a maximum of three different symbols.at n=33A056504
• a(n) = (3^(2^n) + 1)/2 = A059919(n)/2, n >= 0.at n=4A059917
• Largest prime factor of 9^(2n)+1 (A063270).at n=4A063271
• Zsigmondy numbers for a = 3, b = 1: Zs(n, 3, 1) is the greatest divisor of 3^n - 1^n (A024023) that is relatively prime to 3^m - 1^m for all positive integers m < n.at n=31A064079
• Largest prime factor of 3^n + 1.at n=16A074476
• Largest prime factor of 3^n - 1.at n=31A074477
• Binomial transform of Jacobsthal gap sequence (A080924).at n=16A080925
• Table T(m,n) = (3^m + 5^n)/2, for m, n = 0, 2, 4, 6, ... read by antidiagonals downwards.at n=44A081458
• a(n) = (3^(2*n) + 1) / 2.at n=8A083884
• Primes of the form (3^k-1)/2 or (3^k+1)/2.at n=6A088553
• Primes of the form (3^m + 1)/2.at n=3A093625
• Primes of the form (k^4 + 1)/2.at n=16A096170
• Duplicate of A088553.at n=6A096724
• a(n) = 3*a(n-1) + a(n-2) - 3*a(n-3).at n=16A103425
• Starting with the fraction 1/1, the prime numerators of fractions built according to the rule: add top and bottom to get the new bottom, add top and 4 times bottom to get the new top.at n=5A111009
• Triangle read by rows: row n contains n terms of the arithmetic progression having first term 1 and common difference 2[n^(n-1)-1]/(n-1).at n=38A111568
• Number of set partitions with at most 3 blocks; number of Dyck paths of height at most 4; dimension of space of symmetric polynomials in 3 noncommuting variables.at n=17A124302