A010697 - OEIS

%I #57 Mar 05 2024 11:25:07

%S 2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,

%T 2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,2,7,

%U 2,7,2,7,2,7,2,7,2,7,2,7,2

%N Period 2: repeat (2,7).

%C Continued fraction expansion of A176054. - _R. J. Mathar_, Mar 08 2012

%C Decimal expansion of 3/11. - _Franklin T. Adams-Watters_, Nov 21 2018

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,1).

%F G.f.: (2+7x)/((1-x)(1+x)). - _R. J. Mathar_, Nov 21 2011

%F a(n) = A010888(2^n+5^n) = A010888(A074600(n)). - _Peter M. Chema_, Jul 13 2016

%F E.g.f.: 7*sinh(x) + 2*cosh(x). - _Ilya Gutkovskiy_, Jul 14 2016

%F a(n) = 14/a(n-1). - _Nicolas Bělohoubek_, Nov 11 2021

%t Table[-5/2*(-1)^n + 9/2, {n, 0, 120}] (* or *)

%t Table[7 Mod[n, 2] + 2 Mod[(n + 1), 2], {n, 0, 120}] (* or *)

%t CoefficientList[Series[(2 + 7 x)/((1 - x) (1 + x)), {x, 0, 120}], x] (* or *)

%t Table[NestWhile[Total@ IntegerDigits@ # &, 2^n + 5^n, IntegerLength@ # > 1 &], {n, 0, 120}] (* _Michael De Vlieger_, Jul 13 2016 *)

%o (PARI) a(n)=if(n%2,7,2) \\ _Charles R Greathouse IV_, Oct 07 2015

%Y Cf. A010888, A074600.

%K nonn,easy

%O 0,1

%A _N. J. A. Sloane_.