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%I #39 Dec 31 2023 10:21:29
%S 4,24,44,64,84,104,124,144,164,184,204,224,244,264,284,304,324,344,
%T 364,384,404,424,444,464,484,504,524,544,564,584,604,624,644,664,684,
%U 704,724,744,764,784,804,824,844,864,884,904,924,944,964,984,1004,1024,1044
%N a(n) = 20*n - 16.
%C Multiples of 4 with the unit digit equal to 4.
%C Positive integers that are the product of two integers ending with 2 (see A017293). - _Stefano Spezia_, Jul 25 2021
%H Vincenzo Librandi, <a href="/A139245/b139245.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) + 20.
%F a(n) = 4*A016861(n-1). - _Wesley Ivan Hurt_, Jan 17 2014
%F From _Stefano Spezia_, Jul 25 2021: (Start)
%F O.g.f.: 4*x*(1 + 4*x)/(1 - x)^2.
%F E.g.f.: 16 + 4*exp(x)*(5*x - 4).
%F a(n) = 2*a(n-1) - a(n-2) for n > 2. (End)
%p A139245:=n->20*n-16; seq(A139245(n), n=1..100); # _Wesley Ivan Hurt_, Jan 17 2014
%t Range[4, 1500, 20] (* _Vladimir Joseph Stephan Orlovsky_, Jun 01 2011 *)
%o (Magma) [20*n-16: n in [1..60]]; // _Vincenzo Librandi_, Jun 19 2011
%o (PARI) a(n)=20*n-16 \\ _Charles R Greathouse IV_, Aug 25 2014
%Y Subsequence of A034709, together with A017281, A017293, A139222, A017329, A139249, A139264, A139279 and A139280.
%Y Cf. A017293.
%K easy,nonn
%O 1,1
%A _Odimar Fabeny_, Jun 06 2008
%E More terms from _Reinhard Zumkeller_, Jun 22 2008
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