Вариант 1[/b]
a_(n)=6n-1
а) a_(4)=6*4-1=23,
б) a_(12)=6*12-1=71,
в) a_(100)=6*100-1=599,
г) a_(k)=6k-1,
д) a_(k+1)=6*(k+1)-1=6k+6-1=6k+5.
[b]Вариант 2[/b]
a_(n)=5n+2
а) a_(4)=5*4+2=22,
б) a_(12)=5*12+2=62,
в) a_(100)=5*100+2=502,
г) a_(k)=5k+2,
д) a_(k+1)=5*(k+1)+2=5k+5+2=5k+7.