Question

Aflati locul pe care il ocupa 2013 in sirul : 3 , 11 , 13 , 21 , 23 , 31 ... ( raspuns concret)dau funda

Answer 1

[tex]a_n=\frac{1}{2}(10n+3(-1)^{n}-1)\\10n+3(-1)^{n}-1=4026\\10n+3(-1)^{n}=4027\\ Presupunem\ n=impar\\10n=4030\\n=403[/tex]