1397419

Appears in sequences

• Cyclotomic polynomials at x=-2.at n=33A020501
• a(n) = (lcm_{k=0..n} (2^k + 1))/(lcm_{k=0..n-1} (2^k + 1)).at n=32A066845
• Sarrus numbers k such that k-1 and k+1 have the same number of prime divisors (counted with multiplicity).at n=14A086806
• Sylvester-Jacobsthal cyclotomic numbers.at n=32A105603
• a(n) = Sum_{k=floor((n+1)/2)..n} J(k+1), J(k) = A001045(k).at n=20A129362
• Numbers representable as Phi(k,2), the k-th cyclotomic polynomial evaluated at 2, for some k>0.at n=39A153601
• Numbers k (between 2^(m-1) and 2^m) such that 2^(k-1) == 1 (mod k) and 2^(k-1-m) == k - 2^p (mod k) for some p > 0 with 2^p < k.at n=27A167612
• Pseudoprimes to base 2 of the form 4k+3.at n=39A177884
• Composite numbers n such that n == 3 (mod 8) and 2^((n-1)/2) == -1 (mod n).at n=4A244628
• a(n) = (1^n + (-2)^n + 4^n)/3.at n=11A245489
• Fermat pseudoprimes that are not Carmichael numbers and have only composite XOR couples as defined in A182108.at n=13A252944
• Composite numbers k == 3 (mod 4) such that (1 + i)^k == 1 - i (mod k), where i = sqrt(-1).at n=12A270697
• The "non-residue" pseudoprimes: odd composite numbers n such that b(n)^((n-1)/2) == -1 (mod n), where base b(n) = A020649(n).at n=27A307767
• a(n) = (q^2-q+1)/3 where q = 2^(2*n+1) = A004171(n).at n=5A345963
• Odd composite numbers k such that 2^((k-1)/2) == -1 (mod k).at n=20A356638