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.
%I A231643 #19 Jan 07 2021 20:11:08
%S A231643 10,15,25,45,85,165,325,645,1285,2565,5125,10245,20485,40965,81925,
%T A231643 163845,327685,655365,1310725,2621445,5242885,10485765,20971525,
%U A231643 41943045,83886085,167772165,335544325,671088645,1342177285,2684354565,5368709125,10737418245
%N A231643 a(n) = 5*2^n + 5.
%C A231643 For n > 2, decimals given by base 2 pattern: 101...zeros...101.
%C A231643 The ratio between a(n) and a(n+1) tends to 1/2.
%C A231643 Sum(1/a(i), i=0..infinity) = ( psi_2^(0)( 1 - i*Pi/log(2) ) + i*Pi ) / log(32) = 0.252899956069688841838263949451..., where psi_q^(m)(.) is the m-th derivative of the q-digamma function. [_Bruno Berselli_, Nov 15 2013]
%H A231643 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2).
%F A231643 a(n) = 5*A000051(n). - _Philippe Deléham_, Nov 15 2013
%F A231643 G.f.: 5*(2-3*x)/((1-x)*(1-2*x)). - _Philippe Deléham_, Nov 15 2013
%F A231643 a(n) = 3*a(n-1)-2*a(n-2) for n>1, a(0)=10, a(1)=15. - _Philippe Deléham_, Nov 15 2013
%t A231643 Table[5*2^n + 5, {n, 0, 50}] (* _T. D. Noe_, Nov 15 2013 *)
%Y A231643 Cf. A000079 (powers of 2), A000051.
%K A231643 nonn,easy
%O A231643 0,1
%A A231643 _Przemyslaw Wcislo_, Nov 12 2013