seq.c

#include <stdio.h>
#include <stdlib.h>

int main() {
    int i, n, l;
    int *output;

    printf("Enter first number: ");
    scanf("%d",&n);
    printf("Enter sequence length: ");
    scanf("%d",&l);
    output = malloc(sizeof(int)*l);

    for (i = 0; i < l; i++){
        int tmp = n;
        int sum = 0;
        do {
            int fact = 1;
            int digit = tmp%10;
            while(digit)
                fact *= digit--;
            sum += fact;
        } while (tmp/=10);
        output[i] = n = sum;
    }

    for (i = 0; i < l; i++)
        printf("%d:%d\n", i, output[i]);

    free(output);
    return 0;
}