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 A227644 Perfect powers equal to the sum of 2 factorial numbers. 9
 4, 8, 25, 121, 144, 5041 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 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 LINKS Giovanni Resta, Decompositions of a(1)-a(6) EXAMPLE 5041 = 71^2 = 1! + 7!. PROG (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; } CROSSREFS Cf. A114377, A227645, A227646, A227647, A227648, A227649, A227650, A227651, A065433, A085692. Sequence in context: A046736 A174171 A262042 * A074188 A126733 A297695 Adjacent sequences:  A227641 A227642 A227643 * A227645 A227646 A227647 KEYWORD nonn,more AUTHOR Giovanni Resta, Jul 19 2013 STATUS approved

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Last modified July 23 16:14 EDT 2019. Contains 325258 sequences. (Running on oeis4.)