72413domain: NAppears in sequencesa(n) = floor(a(n-1)*(Pi-1)); a(1) = 1.at n=15A063457Numbers n=2*k-1 where Sum_{j=1..k} (-1)^(j+1) * d(2*j-1) achieves a new record, with d(n) = number of divisors of n (A000005).at n=26A318737