A139280 - OEIS

%I #35 Feb 16 2024 01:27:49

%S 9,99,189,279,369,459,549,639,729,819,909,999,1089,1179,1269,1359,

%T 1449,1539,1629,1719,1809,1899,1989,2079,2169,2259,2349,2439,2529,

%U 2619,2709,2799,2889,2979,3069,3159,3249,3339,3429,3519,3609,3699,3789,3879,3969

%N a(n) = 90*n - 81.

%C Multiples of 9 with final digit 9.

%H Vincenzo Librandi, <a href="/A139280/b139280.txt">Table of n, a(n) for n = 1..2000</a>

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

%F a(n) = a(n-1) + 90.

%F From _G. C. Greubel_, Jul 18 2017: (Start)

%F G.f.: 9*(19*x-9)/(x-1)^2.

%F E.g.f.: 9*(10*x - 9)*exp(x). (End) [G.f. corrected by _Georg Fischer_, May 12 2019]

%t Table[90*n-81, {n, 0, 50}] (* _G. C. Greubel_, Jul 18 2017 *)

%o (Magma) [90*n-81: n in [1..50]]; // _Vincenzo Librandi_, Jun 19 2011

%o (PARI) for(n=1, 1e2, a=90*n-81; print1(a, ", ")) \\ _Felix Fröhlich_, Jul 07 2014

%Y Subsequence of A034709, together with A017281, A017293, A139222, A139245, A017329, A139249, A139264 and A139279.

%K easy,nonn

%O 1,1

%A _Odimar Fabeny_, Jun 06 2008

%E More terms from _Reinhard Zumkeller_, Jun 22 2008