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 A139613 #25 Apr 04 2024 15:38:49 %S A139613 13,91,169,247,325,403,481,559,637,715,793,871,949,1027,1105,1183, %T A139613 1261,1339,1417,1495,1573,1651,1729,1807,1885,1963,2041,2119,2197, %U A139613 2275,2353,2431,2509,2587,2665,2743,2821,2899,2977,3055,3133 %N A139613 a(n) = 78*n + 13. %C A139613 Numbers of the 13th column of positive numbers in the square array of nonnegative and polygonal numbers A139600. Also, numbers of the 13th column in the square array A057145. %H A139613 Vincenzo Librandi, <a href="/A139613/b139613.txt">Table of n, a(n) for n = 0..5000</a> %H A139613 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1). %F A139613 From _Elmo R. Oliveira_, Apr 03 2024: (Start) %F A139613 G.f.: 13*(1+5*x)/(x-1)^2. %F A139613 E.g.f.: 13*exp(x)*(1 + 6*x). %F A139613 a(n) = 13*A016921(n). %F A139613 a(n) = 2*a(n-1) - a(n-2) for n >= 2. (End) %t A139613 78*Range[0, 50] + 13 (* _Paolo Xausa_, Apr 04 2024 *) %o A139613 (Magma) [13*(6*n + 1): n in [0..60]]; // _Vincenzo Librandi_, Jul 23 2011 %o A139613 (PARI) a(n)=78*n+13 \\ _Charles R Greathouse IV_, Oct 05 2011 %Y A139613 Cf. A016921, A057145, A139600. %K A139613 easy,nonn %O A139613 0,1 %A A139613 _Omar E. Pol_, Apr 27 2008