21228

Appears in sequences

• Numbers k such that 129*2^k-1 is prime.at n=38A050590
• (-1)sigma sociable number of order 2: (-1)sigma((-1)sigma(x))=x, but (-1)sigma(x)<>x, where if x=Product p(i)^r(i) then (-1)sigma(x)=Product (-1+Sum p(i)^s(i), s(i)=1 to r(i)); (-1)sigma(1)=1.at n=5A051152
• Row sums of triangle A119935 (numerator triangle for certain rationals).at n=5A119934
• a(n) is the smallest number k such that d(1)*1! + d(2)*2! + ... + d(p)*p! = n^2, where d(i) are the decimal digits of k.at n=31A198095
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 581", based on the 5-celled von Neumann neighborhood.at n=27A273071
• E.g.f.: -exp(2*x)*LambertW(-x).at n=6A277485
• Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f. -exp(k*x)*LambertW(-x).at n=42A294411
• E.g.f. A(x) satisfies A(x) = 1 - 2 * log(1-x) * A(-log(1-x)).at n=5A355098