648270

Appears in sequences

• a(n) = 21*a(n-2) + 7*a(n-3), with a(0)=0, a(1)=3, and a(2)=6.at n=9A215492
• a(n) = Sum_{k=1..n} sigma( (n/gcd(k,n))^3 ).at n=27A372998