1720110

Appears in sequences

• a(1)=1; for n>1, a(n) is the smallest positive integer for which sigma(a(n)) is a proper multiple of sigma(a(n-1)).at n=21A237352
• Triangle read by rows: denominator of h(n-k)*h(k)/h(n) where h(x) = zeta(2*x)*(4^x-2), 0<=k<=n.at n=29A246052
• Triangle read by rows: denominator of h(n-k)*h(k)/h(n) where h(x) = zeta(2*x)*(4^x-2), 0<=k<=n.at n=34A246052