1:

uses crt;

var n,i,t:integer;

begin

clrscr;

readln(n);

t:=0;

for i:=1 to n do

t:=t+i*i;

write(t);

readln;

end.

2

program bt2;

var i,n,t:integer;

begin

readln(n);

s:=0;

for i:=1 to n do

if i mod 2 = 1 then s:=s+i;

readln;

end.

Câu 1:

program Tinhtong:

var

     n, i, sum: integer;

begin

     write('Nhap n: ');

     readln(n);

     sum := 0;

     for i := 2 to n do

     begin

          if i mod 2 = 0 then

          begin

               sum := sum + i;

          end;

     end;

     writeln('Tong cac so chan tu 2 toi ', n, ' la ', sum);

     readln; 

end.

Câu 2:

program Tinhtong:

var

     n, i, sum: integer;

begin

     write('Nhap n: ');

     readln(n);

     sum := 0;

     for i := 1 to n do

     begin

          if i mod 2 = 1 then

          begin

               sum := sum + i;

          end;

     end;

     writeln('Tong cac so le tu 1 toi ', n, ' la ', sum);

     readln;

end.

Câu 1: 
uses crt;
var s,i,n:integer;
begin clrscr;
s:=0;
write('Nhap n: ');readln(n);
for i:=1 to n do
if i mod 2 <> 0 then inc(s,i);
write('Tong cac so le tu 1 den ',n,' la: ',s);
readln
end.

Câu 2:
uses crt;
var s,i,n:integer;
begin clrscr;
s:=0;
write('Nhap n: ');readln(n);
for i:=1 to n do
if i mod 2 = 0 then inc(s,i);
write('Tong cac so le tu 1 den ',n,' la: ',s);
readln
end.

Câu 1: 

uses crt;

var n,i:integer;

s:real;

begin

clrscr;

write('Nhap n='); readln(n);

s:=1;

for i:=1 to n do

s:=s*i;

writeln(s);

readln;

end.

Câu 2: 

uses crt;

var t,i,n:integer;

begin

clrscr;

write('Nhap n='); readln(n);

t:=0;

for i:=1 to n do

t:=t+i;

writeln(t);

readln;

end.

Bài 2 dùng công thức n*(n+1)/2

Uses crt;

var n,i,s: integer;

begin clrscr;

readln(n);

for i:=1 to n do s:=s+1/i;

writeln(s);

readln;

end.

Sửa đề: S=1/1+1/2+1/3+...+1/n

uses crt;

var n,i:integer;

s:real;

begin

clrscr;

write('Nhap n='); readln(n);

s:=0;

for i:=1 to n do 

  s:=s+1/i;

writeln(s:4:2);

readln;

end.

program tong;

uses crt;

var n,i:integer;

t:longint;

begin

clrscr;

write('nhap n:'); readln(n);

t:=0;

for i:=1 to n do 

  t:=t+1/i;

writeln(t);

readln;

end.