25421

Appears in sequences

• Equal count of primes congruent to 1 mod 4 and 3 mod 4 associated with primes in A007351 (the zero beginning the sequence indicates the prime 2).at n=35A092198
• a(0) = a(1) = 1. a(n) = a(n-1) + a(n - b(n)), where b(n) is smallest prime dividing n.at n=26A137808
• Number of (n+2) X (1+2) 0..1 arrays with each 3 X 3 subblock having clockwise perimeter pattern 00000001 00000101 or 00001001.at n=7A260241
• T(n,k)=Number of (n+2)X(k+2) 0..1 arrays with each 3X3 subblock having clockwise perimeter pattern 00000001 00000101 or 00001001.at n=28A260248
• T(n,k)=Number of (n+2)X(k+2) 0..1 arrays with each 3X3 subblock having clockwise perimeter pattern 00000001 00000101 or 00001001.at n=35A260248
• Number of set-systems covering a subset of {1..n} where every two covered vertices appear together in some edge (cointersecting).at n=4A327039
• a(n) = digsum(2^a(n-1)) with a(0) = 0.at n=31A330822