Sum squares and square sums

The sum of the squares of the first ten natural numbers is,

1² + 2² + ... + 10² = 385

The square of the sum of the first ten natural numbers is,

(1 + 2 + ... + 10)² = 55² = 3025

Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 - 385 = 2640.

Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.

.syntax unified

.equ limit,100

number .req r4
sumsq .req r5
sqsum .req r6
tmp .req r7

.section .rodata
 .align 2
string:
 .asciz "%d\n"
.text
 .align 2
 .global main
 .type main, %function
main:
 stmfd sp!, {r4-r7, lr}
 mov sqsum, 0
 mov sumsq, 0
 ldr number, =limit
loop:
 mul tmp, number, number
 add sqsum, sqsum, tmp
# decrement number and loop or exit
 subs number, number, 1
 beq end_loop
 b loop
end_loop:
 ldr number, =limit
 add number, number, 1
 ldr sumsq, =limit
 mul sumsq, sumsq, number
 lsr sumsq, sumsq, 1
 mul sumsq, sumsq, sumsq
last:
 sub tmp, sumsq, sqsum 
 mov r1, tmp
 ldr r0, =string         @ store address of start of string to r0
 bl printf

 mov r0, 0
 ldmfd sp!, {r4-r7, pc}
 mov r7, 1     @ set r7 to 1 - the syscall for exit
 swi 0     @ then invoke the syscall from linux