22261

Appears in sequences

• Strong pseudoprimes to base 14.at n=10A020240
• Strong pseudoprimes to base 83.at n=15A020309
• a(n) = Sum_{k=0,1,2,...,n-4,n-2,n-1} a(k); a(n-3) is not a summand, with a(0)=0, a(1)=1, a(2)=3.at n=17A049859
• a(n) = n^4/2 - n^3 + 3*n^2/2 - n + 1 = (n^2 + 1)*(n^2 - 2*n + 2)/2.at n=15A058919
• Downward vertical of triangular spiral in A051682.at n=35A081272
• (Prime(prime(n))^2+1)/2.at n=14A092773
• Appearance radii of visible vectors in the medial axis test mask for the Euclidean distance in Z^2.at n=20A171988
• Indices of hexagonal numbers (A000384) which are also centered triangular numbers (A005448).at n=4A254283
• a(n) = Product p_{n*i}^e_i if the prime factorization of n is Product p_i^e_i.at n=14A352028
• Centered square numbers which are semiprime.at n=45A371016