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 A139618 #24 Apr 08 2024 17:47:42
%S A139618 18,171,324,477,630,783,936,1089,1242,1395,1548,1701,1854,2007,2160,
%T A139618 2313,2466,2619,2772,2925,3078,3231,3384,3537,3690,3843,3996,4149,
%U A139618 4302,4455,4608,4761,4914,5067,5220,5373,5526,5679,5832,5985
%N A139618 a(n) = 153*n + 18.
%C A139618 Numbers of the 18th column of positive numbers in the square array of nonnegative and polygonal numbers A139600. Also, numbers of the 18th column in the square array A057145.
%H A139618 Vincenzo Librandi, <a href="/A139618/b139618.txt">Table of n, a(n) for n = 0..5000</a>
%H A139618 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A139618 From _Elmo R. Oliveira_, Apr 04 2024: (Start)
%F A139618 G.f.: 9*(2+15*x)/(x-1)^2.
%F A139618 E.g.f.: 9*exp(x)*(2 + 17*x).
%F A139618 a(n) = 9*(A008599(n) + 2).
%F A139618 a(n) = 2*a(n-1) - a(n-2) for n >= 2. (End)
%t A139618 153*Range[0,40]+18 (* or *) LinearRecurrence[{2,-1},{18,171},40] (* _Harvey P. Dale_, May 25 2016 *)
%o A139618 (Magma) [9*(17*n + 2): n in [0..50]]; // _Vincenzo Librandi_, Jul 23 2011
%o A139618 (PARI) a(n)=153*n+18 \\ _Charles R Greathouse IV_, Oct 05 2011
%Y A139618 Cf. A008599, A057145, A139600.
%K A139618 easy,nonn
%O A139618 0,1
%A A139618 _Omar E. Pol_, May 21 2008