A017209 a(n) = 9*n + 4.

4, 13, 22, 31, 40, 49, 58, 67, 76, 85, 94, 103, 112, 121, 130, 139, 148, 157, 166, 175, 184, 193, 202, 211, 220, 229, 238, 247, 256, 265, 274, 283, 292, 301, 310, 319, 328, 337, 346, 355, 364, 373, 382, 391, 400, 409, 418, 427, 436, 445, 454, 463, 472, 481

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

Numbers whose digital root is 4. - L. Edson Jeffery, Nov 26 2016

References

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

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..5000
• Tanya Khovanova, Recursive Sequences
• Index entries for linear recurrences with constant coefficients, signature (2,-1).

Crossrefs

Cf. A008591, A010888, A017185, A017197.

Programs

Magma

[9*n+4: n in [0..60]]; // Vincenzo Librandi, Jul 23 2011

Mathematica

Range[4, 1000, 9] (* Vladimir Joseph Stephan Orlovsky, May 28 2011 *)

PARI

forstep(n=4,500,9,print1(n", ")) \\ Charles R Greathouse IV, May 28 2011

Formula

G.f.: (4 + 5*x)/(x - 1)^2. - R. J. Mathar, Jul 14 2016

A010888(a(n)) = 4. - L. Edson Jeffery, Nov 26 2016

E.g.f.: exp(x)*(4 + 9*x). - Stefano Spezia, Dec 25 2022