18193

Appears in sequences

• a(n) = a(1) + a(2) + ... + a(n-1) - a(m) for n >= 4, where m = 2*n - 3 - 2^(p+1) and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = a(2) = 1 and a(3) = 4.at n=16A049896
• Numbers k such that (3*2^k+1)^2-2 is prime.at n=19A100912
• Numbers n such that p(9n) is prime, where p(n) is the number of partitions of n.at n=26A114169
• a(n) = (2^(semiprime(n)-1)) modulo (semiprime(n)^2).at n=45A115948
• Number of planar n X n X n binary triangular grids symmetric both under 120-degree rotation and reflection with no more than 1 one in any 3 X 3 X 3 subtriangle.at n=23A153901
• a(n) is the sum of all possible pairs of the first n primes.at n=21A162867
• Number of binary strings of length n which have the same number of 00 and 01 substrings.at n=17A163493
• Number of (n+1) X (n+1) 0..2 arrays with every 2 X 2 subblock summing to 4 and no 2 X 2 subblock having exactly two nonzero entries.at n=7A251142
• Composites whose prime factorization in base 11 is an anagram of the number in base 11.at n=2A260054
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 734", based on the 5-celled von Neumann neighborhood.at n=32A273455
• Sum of terms in level n of TRIP - Stern sequence associated with permutation triple (e,e,132).at n=9A278613
• a(n) is the first composite number having the same base-n digits as its prime factors (with multiplicity), excluding zero digits (or 0 if no such composite number exists).at n=9A278981
• a(n) is the smallest composite number having the same base-n digits (both type and quantity) as its prime factors (with multiplicity).at n=9A281336
• Compound filter: a(n) = P(sigma(n), sigma(2n)), where P(n,k) is sequence A000027 used as a pairing function, and sigma is the sum of divisors (A000203).at n=32A286359
• Compound filter: a(n) = P(sigma(n), sigma(2n)), where P(n,k) is sequence A000027 used as a pairing function, and sigma is the sum of divisors (A000203).at n=34A286359
• Compound filter: a(n) = P(sigma(n), sigma(2n)), where P(n,k) is sequence A000027 used as a pairing function, and sigma is the sum of divisors (A000203).at n=46A286359
• Expansion of e.g.f. Product_{k>=1} 1/(1 - x^prime(k))^(1/prime(k)).at n=8A318913
• MM-numbers of capturing, non-nesting multiset partitions (with empty parts allowed).at n=33A326260
• Odd composite integers m such that U(m)^2 == 1 (mod m) and V(m) == 7 (mod m), where U(m) and V(m) are the m-th generalized Lucas and Pell-Lucas numbers of parameters a=7 and b=-1, respectively.at n=28A337630
• Odd composite integers m such that A086902(m) == 7 (mod m).at n=38A338079