%I #42 Oct 05 2024 14:05:39

%S 4,13,22,31,40,49,58,67,76,85,94,103,112,121,130,139,148,157,166,175,

%T 184,193,202,211,220,229,238,247,256,265,274,283,292,301,310,319,328,

%U 337,346,355,364,373,382,391,400,409,418,427,436,445,454,463,472,481

%N a(n) = 9*n + 4.

%C Numbers whose digital root is 4. - _L. Edson Jeffery_, Nov 26 2016

%D R. K. Guy, Unsolved Problems in Number Theory, Springer, 1st edition, 1981. See section D5.

%H Vincenzo Librandi, <a href="/A017209/b017209.txt">Table of n, a(n) for n = 0..5000</a>

%H Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).

%F G.f.: (4 + 5*x)/(x - 1)^2. - _R. J. Mathar_, Jul 14 2016

%F A010888(a(n)) = 4. - _L. Edson Jeffery_, Nov 26 2016

%F E.g.f.: exp(x)*(4 + 9*x). - _Stefano Spezia_, Dec 25 2022

%t Range[4, 1000, 9] (* _Vladimir Joseph Stephan Orlovsky_, May 28 2011 *)

%o (PARI) forstep(n=4,500,9,print1(n", ")) \\ _Charles R Greathouse IV_, May 28 2011

%o (Magma) [9*n+4: n in [0..60]]; // _Vincenzo Librandi_, Jul 23 2011

%Y Cf. A008591, A010888, A017185, A017197.

%K nonn,easy

%O 0,1

%A _N. J. A. Sloane_