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 A171507 #12 Sep 08 2022 08:45:50 %S A171507 0,0,1,6,17,42,93,198,409,834,1685,3390,6801,13626,27277,54582,109193, %T A171507 218418,436869,873774,1747585,3495210,6990461,13980966,27961977, %U A171507 55924002,111848053,223696158,447392369,894784794,1789569645,3579139350,7158278761,14316557586 %N A171507 a(n) = (5*2^(n+1)-9-(-1)^n)/6-2*n. %H A171507 Vincenzo Librandi, <a href="/A171507/b171507.txt">Table of n, a(n) for n = 0..1000</a> %H A171507 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (3, -1, -3, 2). %F A171507 a(n) = 3*a(n-1)-a(n-2)-3*a(n-3)+2*a(n-4). G.f.: x^2*(1+3*x)/((1+x)*(1-2*x)*(1-x)^2). %F A171507 a(n) = A084640(n) - A042948(n). %F A171507 a(n+1)-2*a(n) = A042948(n+1). %F A171507 First differences: a(n+1)-a(n) = A084640(n). %F A171507 Last digits: a(n) == a(n+10) (mod 10), n>=1. %p A171507 A171507:=n->(5*2^(n+1)-9-(-1)^n)/6 -2*n: seq(A171507(n), n=0..50); # _Wesley Ivan Hurt_, May 03 2017 %o A171507 (Magma) [(5*2^(n+1)-9-(-1)^n)/6 -2*n: n in [0..40]]; // _Vincenzo Librandi_, Aug 05 2011 %Y A171507 Cf. A042948, A084640. %K A171507 nonn,easy %O A171507 0,4 %A A171507 _Paul Curtz_, Dec 10 2009 %E A171507 Edited and extended by _R. J. Mathar_, Dec 15 2009