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 A135168 #16 Sep 08 2022 08:45:32
%S A135168 4,17,87,503,3123,20207,134067,903983,6162243,42326927,292300947,
%T A135168 2026334063,14085963363,98111316047,684331387827,4778093469743,
%U A135168 33385561572483,233393582711567,1632228682858707,11417969834487023,79887637217085603,559022711703937487
%N A135168 a(n) = 7^n + 5^n + 3^n + 2^n.
%C A135168 Constants (7,5,3,2) are the prime numbers in decreasing order.
%H A135168 Vincenzo Librandi, <a href="/A135168/b135168.txt">Table of n, a(n) for n = 0..200</a>
%H A135168 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (17,-101,247,-210).
%F A135168 From _G. C. Greubel_, Sep 30 2016: (Start)
%F A135168 a(n) = 17*a(n-1) - 101*a(n-2) + 247*a(n-3) - 210*a(n-4).
%F A135168 G.f.: (4 - 51*x + 202*x^2 - 247*x^3)/((1 -2*x)*(1 -3*x)*(1 -5*x)*(1 -7*x)).
%F A135168 E.g.f.: exp(7*x) + exp(5*x) + exp(3*x) + exp(2*x). (End)
%e A135168 a(4) = 3123 = 7^4 + 5^4 + 3^4 + 2^4 = 2401 + 625 + 81 + 16.
%p A135168 A135168:=n->7^n+5^n+3^n+2^n; seq(A135168(k), k=0..100); # _Wesley Ivan Hurt_, Nov 05 2013
%t A135168 Table[7^n+5^n+3^n+2^n, {n,0,100}] (* _Wesley Ivan Hurt_, Nov 05 2013 *)
%t A135168 LinearRecurrence[{17, -101, 247, -210}, {4, 17, 87, 503}, 25] (* _G. C. Greubel_, Sep 30 2016 *)
%o A135168 (Magma) [7^n+5^n+3^n+2^n: n in [0..25]]; // _Vincenzo Librandi_, Jun 11 2011
%o A135168 (PARI) a(n)=7^n+5^n+3^n+2^n \\ _Charles R Greathouse IV_, Sep 30 2016
%Y A135168 Cf. A000079, A000244, A000351, A000420, A001047, A074527, A007689, A135158, A135159, A135160, A001551.
%K A135168 easy,nonn
%O A135168 0,1
%A A135168 _Omar E. Pol_, Nov 21 2007
%E A135168 Edited by _N. J. A. Sloane_, Dec 14 2007