cp's OEIS Frontend

A258621 Decimal expansion of sum(1/A030450).

%I A258621 #11 Jun 06 2015 07:49:16
%S A258621 2,2,5,6,9,4,7,4,5,8,5,2,6,5,9,7,9,5,5,4,6,2,7,3,6,7,2,4,4,4,2,3,4,2,
%T A258621 2,1,0,5,5,9,2,3,6,5,0,8,8,9,3,6,9,5,9,5,3,3,4,6,0,0,4,9,6,0,9,2,6,7,
%U A258621 5,4,9,2,8,1,7,5,2,2,0,0,6,7,7,6,1,4,8,9,6,2,1,3,3,1,7,7,7,7,7,7,2,8,5,6,4,6
%N A258621 Decimal expansion of sum(1/A030450).
%e A258621 2.2569474585265979554627367244423422105592365088936959533....
%o A258621 (Sage)
%o A258621 def A030450(n) :
%o A258621    return prod((n-i+1)^(2^i) for i in (1..n))
%o A258621 N(sum(1/A030450(n) for n in (0..9)), digits=106)
%o A258621 (C)
%o A258621 #include <stdio.h>
%o A258621 #include <mpfr.h>
%o A258621 #define dBIT   512
%o A258621 #define dLIST  n, t, u
%o A258621 int main (void) {
%o A258621 mpfr_t dLIST;
%o A258621 mpfr_rnd_t trnd;
%o A258621 unsigned int i;
%o A258621 trnd = MPFR_RNDU;
%o A258621 mpfr_inits2 (dBIT, dLIST, (mpfr_ptr) 0);
%o A258621 mpfr_set_d (n, 1.0, trnd);
%o A258621 mpfr_set_d (t, 1.0, trnd);
%o A258621 for (i = 1; i <= 9; i++) {
%o A258621     mpfr_mul_ui (t, t, i, trnd);
%o A258621     mpfr_mul (t, t, t, trnd);
%o A258621     mpfr_set_d (u, 1.0, trnd);
%o A258621     mpfr_div (u, u, t, trnd);
%o A258621     mpfr_add (n, n, u, trnd);
%o A258621 }
%o A258621 mpfr_printf ("%.106Rg", n);
%o A258621 mpfr_clears (dLIST, (mpfr_ptr) 0);
%o A258621 return 0;
%o A258621 }
%Y A258621 Cf. A030450.
%K A258621 nonn,cons
%O A258621 1,1
%A A258621 _Jani Melik_, Jun 06 2015