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 A147601 #19 Oct 25 2022 03:35:13
%S A147601 7,4,21,8,35,12,49,16,63,20,77,24,91,28,105,32,119,36,133,40,147,44,
%T A147601 161,48,175,52,189,56,203,60,217,64,231,68,245,72,259,76,273,80,287,
%U A147601 84,301,88,315,92,329,96,343,100,357
%N A147601 First differences of A132355.
%H A147601 G. C. Greubel, <a href="/A147601/b147601.txt">Table of n, a(n) for n = 0..1000</a>
%H A147601 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,2,0,-1).
%F A147601 G.f.: ( 7+4*x+7*x^2 ) / ((1-x)*(1+x))^2. - _R. J. Mathar_, Jun 21 2011
%F A147601 a(2*n) = A147587(n).
%F A147601 a(2*n+1) = 4*(n+1).
%F A147601 a(n) = (9 + 5*(-1)^n)*(1+n)/2. - _Colin Barker_, Jun 06 2012
%F A147601 E.g.f.: (1/2)*(5*(1-x)*exp(-x) + 9*(1+x)*exp(x)). - _G. C. Greubel_, Oct 25 2022
%t A147601 Differences[Sort[Table[9n^2+2n,{n,-30,30}]]] (* or *) LinearRecurrence[ {0,2,0,-1},{7,4,21,8},60] (* _Harvey P. Dale_, Jun 04 2017 *)
%o A147601 (Magma) [(9 + 5*(-1)^n)*(1+n)/2: n in [0..60]]; // _G. C. Greubel_, Oct 25 2022
%o A147601 (SageMath) [(9 + 5*(-1)^n)*(1+n)/2 for n in range(61)] # _G. C. Greubel_, Oct 25 2022
%Y A147601 Cf. A132355, A147587.
%K A147601 nonn,easy
%O A147601 0,1
%A A147601 _Paul Curtz_, Nov 08 2008