Question Number 94603 by byaw last updated on 19/May/20
$$\mathrm{List}\:\mathrm{the}\:\mathrm{elements}\:\mathrm{in}\: \\ $$$${C}=\left\{{x}:{x}\:\mathrm{is}\:\mathrm{an}\:{x}^{\mathrm{2}} \leqslant\mathrm{4},\:\mathrm{integer}\right\} \\ $$
Commented by Rasheed.Sindhi last updated on 20/May/20
$${C}=\left\{−\mathrm{2},−\mathrm{1},\mathrm{0},\mathrm{1},\mathrm{2}\right\} \\ $$
Answered by mathmax by abdo last updated on 20/May/20
$$\mathrm{let}\:\mathrm{a}_{\mathrm{n}} =\mathrm{card}\left\{\left(\mathrm{x},\mathrm{y}\right)\in\mathrm{N}^{\mathrm{2}} /\mathrm{x}+\mathrm{2y}\:=\mathrm{n}\right\}\:\:\mathrm{calculate}\:\sum_{\mathrm{n}=\mathrm{0}} ^{\infty} \:\mathrm{a}_{\mathrm{n}} \mathrm{x}^{\mathrm{n}} \\ $$$$\:\mathrm{its}\:\mathrm{a}\:\mathrm{question} \\ $$