A139264 - OEIS

%I #28 Apr 04 2025 16:01:05

%S 7,77,147,217,287,357,427,497,567,637,707,777,847,917,987,1057,1127,

%T 1197,1267,1337,1407,1477,1547,1617,1687,1757,1827,1897,1967,2037,

%U 2107,2177,2247,2317,2387,2457,2527,2597,2667,2737,2807,2877,2947,3017,3087,3157,3227

%N a(n) = 70*n - 63.

%C Multiples of 7 with unit digit equal to 7.

%H Vincenzo Librandi, <a href="/A139264/b139264.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) + 70.

%F From _Elmo R. Oliveira_, Apr 04 2025: (Start)

%F G.f.: 7*x*(1+9*x)/(1-x)^2.

%F E.g.f.: 7*(exp(x)*(10*x - 9) + 9).

%F a(n) = 7*A017281(n-1).

%F a(n) = 2*a(n-1) - a(n-2) for n > 2. (End)

%t 70*Range[50]-63 (* _Harvey P. Dale_, May 06 2019 *)

%o (Magma) [70*n-63: n in [1..50]]; // _Vincenzo Librandi_, Jun 19 2011

%o (PARI) a(n)=70*n-63 \\ _Charles R Greathouse IV_, Aug 25 2014

%Y Subsequence of A034709, together with A017281, A017293, A139222, A139245, A017329, A139249, A139279 and A139280.

%K easy,nonn

%O 1,1

%A _Odimar Fabeny_, Jun 06 2008

%E More terms from _Reinhard Zumkeller_, Jun 22 2008