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Decimal expansion of sum(1/A030450).
1

%I #11 Jun 06 2015 07:49:16

%S 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 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 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 Decimal expansion of sum(1/A030450).

%e 2.2569474585265979554627367244423422105592365088936959533....

%o (Sage)

%o def A030450(n) :

%o return prod((n-i+1)^(2^i) for i in (1..n))

%o N(sum(1/A030450(n) for n in (0..9)), digits=106)

%o (C)

%o #include <stdio.h>

%o #include <mpfr.h>

%o #define dBIT 512

%o #define dLIST n, t, u

%o int main (void) {

%o mpfr_t dLIST;

%o mpfr_rnd_t trnd;

%o unsigned int i;

%o trnd = MPFR_RNDU;

%o mpfr_inits2 (dBIT, dLIST, (mpfr_ptr) 0);

%o mpfr_set_d (n, 1.0, trnd);

%o mpfr_set_d (t, 1.0, trnd);

%o for (i = 1; i <= 9; i++) {

%o mpfr_mul_ui (t, t, i, trnd);

%o mpfr_mul (t, t, t, trnd);

%o mpfr_set_d (u, 1.0, trnd);

%o mpfr_div (u, u, t, trnd);

%o mpfr_add (n, n, u, trnd);

%o }

%o mpfr_printf ("%.106Rg", n);

%o mpfr_clears (dLIST, (mpfr_ptr) 0);

%o return 0;

%o }

%Y Cf. A030450.

%K nonn,cons

%O 1,1

%A _Jani Melik_, Jun 06 2015