18661

Properties

Appears in sequences

• a(n) = Sum_{i=0..2*n} Sum_{j=0..i} T(i, j), where T is given by A026552.at n=10A026567
• Numbers k such that 20^k - 19^k is prime.at n=6A062586
• Number of digits of n!^n! (ultrafactorial numbers).at n=7A073279
• a(n) = (n^3 + 24*n^2 + 65*n + 36)/6.at n=41A087863
• Number of preferential arrangements of n labeled elements when only k <= 3 ranks are allowed.at n=9A101052
• Primes p such that p - q = 24, where q is the previous prime before p; or prime numbers preceded by precisely 23 composite numbers.at n=31A126720
• The smallest prime p that makes the pair p+/-6n both primes while no other pair of p+/-6k+6*n, 0<k<n both primes.at n=57A139602
• Primes congruent to 5 mod 53.at n=38A142535
• Primes congruent to 17 mod 59.at n=36A142744
• Primes congruent to 56 mod 61.at n=37A142854
• Primes p such that continued fraction of (1 + sqrt(p))/2 has period 15: primes in A146338.at n=30A146360
• Primes p such that q*p+-Mod(p,q) are primes, for q=7.at n=26A178387
• Number of nondecreasing arrangements of n+2 numbers in 0..8 with the last equal to 8 and each after the second equal to the sum of one or two of the preceding three.at n=35A190040
• Number of nX5 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 2,3,0,1,4 for x=0,1,2,3,4.at n=5A196490
• Number of nX6 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 2,3,0,1,4 for x=0,1,2,3,4.at n=4A196491
• T(n,k)=Number of nXk 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 2,3,0,1,4 for x=0,1,2,3,4.at n=49A196493
• T(n,k)=Number of nXk 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 2,3,0,1,4 for x=0,1,2,3,4.at n=50A196493
• a(n) = (2*6^(n+1) - 7) / 5.at n=5A233325
• Primes p with q(p) - 1 also prime, where q(.) is the strict partition function (A000009).at n=55A234644
• Primes whose base-6 representation also is the base-3 representation of a prime.at n=21A235469