First number of divisor symmetry n: d(n-k) = d(n+k) for 1 <= k <= n, but d(n-k-1) != d(n+k+1).

A202463

First number of divisor symmetry n: d(n-k) = d(n+k) for 1 <= k <= n, but d(n-k-1) != d(n+k+1).

Terms

    a(0) =4a(1) =9a(2) =216a(3) =30a(4) =20376a(5) =432a(6) =18000a(7) =13338864a(8) =15194736a(9) =866452464a(10) =5175273600a(11) =35399473200

External references