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 A072259 #19 May 17 2025 22:43:20
%S A072259 12,57,261,1173,5205,22869,99669,431445,1856853,7951701,33903957,
%T A072259 144004437,609572181,2572506453,10826896725,45455070549,190410216789,
%U A072259 796000605525,3321441375573,13835521316181,57541108520277,238960527103317,991026480502101
%N A072259 a(n) = ((6*n+37)*4^n - 1)/3.
%C A072259 Related to Collatz function (for n>0). All terms are divisible by 3.
%H A072259 G. C. Greubel, <a href="/A072259/b072259.txt">Table of n, a(n) for n = 0..1000</a>
%H A072259 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (9,-24,16).
%F A072259 G.f.: 3*(4-17*x+12*x^2)/((1-x)*(1-4*x)^2). - _Bruno Berselli_, Dec 16 2011
%F A072259 E.g.f.: ((37 + 24*x)*exp(4*x) - exp(x))/3. - _G. C. Greubel_, Jan 14 2020
%p A072259 seq( ((6*n+37)*4^n -1)/3, n=0..30); # _G. C. Greubel_, Jan 14 2020
%t A072259 LinearRecurrence[{9,-24,16},{12,57,261},30] (* _Harvey P. Dale_, Mar 10 2018 *)
%o A072259 (PARI) a(n)=((6*n+37)*4^n-1)/3 \\ _Charles R Greathouse IV_, Oct 07 2015
%o A072259 (Magma) [((6*n+37)*4^n -1)/3: n in [0..30]]; // _G. C. Greubel_, Jan 14 2020
%o A072259 (Sage) [((6*n+37)*4^n -1)/3 for n in (0..30)] # _G. C. Greubel_, Jan 14 2020
%o A072259 (GAP) List([0..30], n-> ((6*n+37)*4^n -1)/3); # _G. C. Greubel_, Jan 14 2020
%Y A072259 Cf. A072257, A072258, A072260.
%K A072259 nonn,easy
%O A072259 0,1
%A A072259 N. Rathankar (rathankar(AT)yahoo.com), Jul 08 2002
%E A072259 Edited and extended by _Henry Bottomley_, Aug 06 2002
%E A072259 More terms from _Harvey P. Dale_, Mar 10 2018