19/04/26 17:20:18.62 AXvpsest.net
>>306
漸化式： (n+1) S(n+2) = n S(n+1) + 2 S(n),
S(1) = 1, S(2) = 0, S(3) = 1, S(4) = 2/3, S(5) = 1, S(6) = 16/15, S(7) = 11/9,
母関数： x･exp(-2x)/(1-x)^2 = Σ[k=0,∞] S(k) x^k,
s(n) = (n-1)! S(n) は自然数列で、OEIS にある。
漸化式： s(n+2) = n{s(n+1) + 2s(n)},
s(1) = 1, s(2) = 0, s(3) = 2, s(4) = 4, s(5) = 24, s(6) = 128, s(7) = 880,
URLﾘﾝｸ(oeis.org)