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 A139222 #35 Apr 04 2025 16:00:02 %S A139222 3,33,63,93,123,153,183,213,243,273,303,333,363,393,423,453,483,513, %T A139222 543,573,603,633,663,693,723,753,783,813,843,873,903,933,963,993,1023, %U A139222 1053,1083,1113,1143,1173,1203,1233,1263,1293,1323,1353,1383,1413,1443,1473 %N A139222 a(n) = 30*n - 27. %C A139222 Multiples of 3 with the units digit equal to 3. %H A139222 Vincenzo Librandi, <a href="/A139222/b139222.txt">Table of n, a(n) for n = 1..2000</a> %H A139222 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1). %F A139222 a(n) = a(n-1) + 30. %F A139222 From _Elmo R. Oliveira_, Apr 04 2025: (Start) %F A139222 G.f.: 3*x*(1+9*x)/(1-x)^2. %F A139222 E.g.f.: 3*(exp(x)*(10*x - 9) + 9). %F A139222 a(n) = 3*A017281(n-1) = A139280(n)/3. %F A139222 a(n) = 2*a(n-1) - a(n-2) for n > 2. (End) %t A139222 Range[3, 2000, 30] (* _Vladimir Joseph Stephan Orlovsky_, Jun 15 2011 *) %t A139222 30*Range[50]-27 (* or *) NestList[30+#&,3,50] (* _Harvey P. Dale_, Mar 27 2021 *) %o A139222 (Magma) [30*n - 27: n in [1..60]]; // _Vincenzo Librandi_, Jun 17 2011 %o A139222 (PARI) a(n)=30*n-27 \\ _Charles R Greathouse IV_, Aug 25 2014 %Y A139222 Subsequence of A034709, together with A017281, A017293, A139245, A017329, A139249, A139264, A139279 and A139280. %K A139222 nonn,easy %O A139222 1,1 %A A139222 _Odimar Fabeny_, Jun 06 2008 %E A139222 More terms from _Reinhard Zumkeller_, Jun 22 2008