cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A227644 Perfect powers equal to the sum of 2 factorial numbers.

Original entry on oeis.org

4, 8, 25, 121, 144, 5041
Offset: 1

Views

Author

Giovanni Resta, Jul 19 2013

Keywords

Comments

a(7), if it exists, is greater than 10^100.
a(7), if it exists, is greater than 10000!. - Filip Zaludek, Jul 18 2017
a(7), if it exists, is greater than 11750!. - Filip Zaludek, Sep 07 2018
a(7), if it exists, is greater than 20000!. - Filip Zaludek, Nov 04 2020

Examples

			5041 = 71^2 = 1! + 7!.
		

Crossrefs

Programs

  • C
    /* To compile: gcc -Wall -O2 A227644.c -o A227644 -lgmp */
    #include 
    #include 
    #include 
    int main()
    {
       int bsz=256, a=0;
       mpz_t *f, t;
       f = malloc(sizeof(mpz_t) * bsz);
       mpz_init(t); mpz_init(f[0]); mpz_set_ui(f[0], 1);
       while (1)
       {
           a += 1;
           if (a == bsz)
           {
               bsz *= 2;
               f = (mpz_t *) realloc(f, sizeof(mpz_t) * bsz);
           }
           mpz_init(f[a]);
           mpz_mul_ui(f[a], f[a-1], a);
           for (int i=1; i<=a; i++)
           {
               mpz_add(t, f[a], f[i]);
               if (mpz_perfect_power_p(t))
               {
                   gmp_printf("%Zd, ", t);
                   fflush(stdout);
               }
           }
       }
       return 0;
    }

A227651 Perfect powers equal to the sum of 10 factorial numbers.

Original entry on oeis.org

16, 25, 27, 32, 36, 49, 64, 81, 100, 125, 128, 144, 169, 196, 216, 225, 256, 289, 324, 343, 400, 441, 484, 512, 529, 625, 676, 729, 784, 841, 900, 1000, 1024, 1089, 1156, 1225, 1331, 1444, 1521, 1600, 1681, 1728, 1936, 2048, 2187, 2197, 2304, 2401, 2916, 3025
Offset: 1

Views

Author

Giovanni Resta, Jul 19 2013

Keywords

Comments

a(240), if it exists, is larger than 10^50.

Examples

			25411681 = 71^4 = 1! + 7! + 7! + 10! + 10! + 10! + 10! + 10! + 10! + 10!.
		

Crossrefs

Showing 1-2 of 2 results.