220320

Appears in sequences

• Expansion of (1-x)/(1 - x - 2*x^3 + x^4).at n=31A052916
• Least k such that Sum_{i=1..k} gcd(k,i) = n * sigma(k).at n=11A072108
• a(1) = 1, a(2) = 2; for n>2, a(n) = sum_{r=1..n} {sum of all previous terms taken r at a time}.at n=6A089709
• Coefficients in q-expansion of E_2^2, where E_2 is the Eisenstein series shown in A006352.at n=10A281374
• a(n) = Sum_{k=1..n} phi(k) * (floor(n/k)^4 - floor((n-1)/k)^4).at n=35A344600
• a(n) is the smallest number with exactly n divisors that are hoax numbers (A019506).at n=12A357034