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 A017209 #42 Oct 05 2024 14:05:39 %S A017209 4,13,22,31,40,49,58,67,76,85,94,103,112,121,130,139,148,157,166,175, %T A017209 184,193,202,211,220,229,238,247,256,265,274,283,292,301,310,319,328, %U A017209 337,346,355,364,373,382,391,400,409,418,427,436,445,454,463,472,481 %N A017209 a(n) = 9*n + 4. %C A017209 Numbers whose digital root is 4. - _L. Edson Jeffery_, Nov 26 2016 %D A017209 R. K. Guy, Unsolved Problems in Number Theory, Springer, 1st edition, 1981. See section D5. %H A017209 Vincenzo Librandi, <a href="/A017209/b017209.txt">Table of n, a(n) for n = 0..5000</a> %H A017209 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a> %H A017209 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1). %F A017209 G.f.: (4 + 5*x)/(x - 1)^2. - _R. J. Mathar_, Jul 14 2016 %F A017209 A010888(a(n)) = 4. - _L. Edson Jeffery_, Nov 26 2016 %F A017209 E.g.f.: exp(x)*(4 + 9*x). - _Stefano Spezia_, Dec 25 2022 %t A017209 Range[4, 1000, 9] (* _Vladimir Joseph Stephan Orlovsky_, May 28 2011 *) %o A017209 (PARI) forstep(n=4,500,9,print1(n", ")) \\ _Charles R Greathouse IV_, May 28 2011 %o A017209 (Magma) [9*n+4: n in [0..60]]; // _Vincenzo Librandi_, Jul 23 2011 %Y A017209 Cf. A008591, A010888, A017185, A017197. %K A017209 nonn,easy %O A017209 0,1 %A A017209 _N. J. A. Sloane_