A395756 - OEIS

%I #10 May 16 2026 18:10:28

%S 2,1,1,5,8,4,2,7,3,8,9,5,3,0,2,8,6,2,9,3,7,1,1,5,2,5,0,6,8,5,8,4,4,8,

%T 8,9,1,9,4,2,9,4,8,5,4,6,3,6,0,9,0,8,4,9,4,2,1,6,3,8,0,4,2,3,8,4,2,5,

%U 8,7,1,4,2,3,9,1,0,8,6,6,5,0,0,0,9,3,2,0,9,3,3,8,2,8,9,9,3,2,9,5,3,9,2,5,3,0,9,1,7,9,0

%N Decimal expansion of the sum of the reciprocals of the 9-gonal polygorials A084942.

%H Kelvin Voskuijl, <a href="/A395756/b395756.txt">Table of n, a(n) for n = 1..10000</a>

%F Equals (2/7)^(5/14) * BesselI(-5/7, 2*sqrt(2/7)) * Gamma(2/7).

%e 2.115842738953028629371...

%t RealDigits[(2/7)^(5/14) BesselI[-5/7, 2 Sqrt[2/7]] Gamma[2/7], 10, 120][[1]]

%o (PARI) (2/7)^(5/14) * besseli(-5/7, 2*sqrt(2/7)) * gamma(2/7)

%Y Cf. A001113 (of factorials), A070910 (of factorials squared).

%Y Cf. A395536-A395537, A395755-A395759 (pentagonal to 12-gonal).

%Y Cf. A084942.

%K nonn,cons

%O 1,1

%A _Kelvin Voskuijl_, May 05 2026