20/12/13 20:26:31.29 Fq7wqPea.net
>>882
T(n) = 1+2+････+n = n(n+1)/2,
gcd( T(n), T(n+1) ) = gcd( n(n+1)/2, (n+1)(n+2)/2 )
= (n+1)・gcd(n/2, (n+2)/2) = n+1 (n：偶数)
= (n+1)/2・gcd(n, n+2) = (n+1)/2 (n：奇数)
gcd( T(n), T(n+1) )・gcd( T(n+1), T(n+2) ) = (n+1)(n+2)/2 = T(n+1),