0409132人目の素数さん垢版 | 大砲2019/04/26(金) 08:33:36.37ID:BSQr4ZG5 a(n)=3a(n-1)-a(n-2),a(0)=1,a(1)=2 a(n)=1/10((sqrt(5)-5)(-(1/2(3-sqrt(5)))^n)+(5+sqrt(5))(1/2(3+sqrt(5)))^n) n | a(n) 0 | 1 1 | 2 2 | 5 3 | 13 4 | 34 5 | 89 6 | 233 7 | 610 8 | 1597 9 | 4181