A017377 a(n) = 10*n + 9.

9, 19, 29, 39, 49, 59, 69, 79, 89, 99, 109, 119, 129, 139, 149, 159, 169, 179, 189, 199, 209, 219, 229, 239, 249, 259, 269, 279, 289, 299, 309, 319, 329, 339, 349, 359, 369, 379, 389, 399, 409, 419, 429, 439, 449, 459, 469, 479, 489, 499, 509, 519, 529, 539

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

Numbers k such that k^k ends with 9. - Bruno Berselli, Dec 11 2018

References

• Alfred S. Posamentier, Math Charmers, Tantalizing Tidbits for the Mind, Prometheus Books, NY, 2003, pp. 126-127.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..5000
• Tanya Khovanova, Recursive Sequences.
• INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 979.
• Index entries for linear recurrences with constant coefficients, signature (2,-1).

Crossrefs

Cf. A008592, A016897, A017365, A190876.

Programs

Magma

[10*n+9: n in [0..60]]; // Vincenzo Librandi, May 29 2011

Mathematica

Range[9, 1000, 10] (* Vladimir Joseph Stephan Orlovsky, May 28 2011 *)

PARI

a(n)=10*n+9 \\ Charles R Greathouse IV, Feb 12 2017

Sage

def A017377(n): return 10*n+9
print([A017377(n) for n in range(0,54)]) # Stefano Spezia, May 26 2025

Formula

a(n) = 10*n + 9; a(n) = 2*a(n-1) - a(n-2). - Vincenzo Librandi, May 29 2011

G.f.: (9+x)/(x-1)^2. - R. J. Mathar, Oct 16 2015

From Elmo R. Oliveira, Apr 05 2025: (Start)

E.g.f.: exp(x)*(9 + 10*x).

a(n) = A016897(2*n+1). (End)