This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A139264 #28 Apr 04 2025 16:01:05 %S A139264 7,77,147,217,287,357,427,497,567,637,707,777,847,917,987,1057,1127, %T A139264 1197,1267,1337,1407,1477,1547,1617,1687,1757,1827,1897,1967,2037, %U A139264 2107,2177,2247,2317,2387,2457,2527,2597,2667,2737,2807,2877,2947,3017,3087,3157,3227 %N A139264 a(n) = 70*n - 63. %C A139264 Multiples of 7 with unit digit equal to 7. %H A139264 Vincenzo Librandi, <a href="/A139264/b139264.txt">Table of n, a(n) for n = 1..2000</a> %H A139264 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1). %F A139264 a(n) = a(n-1) + 70. %F A139264 From _Elmo R. Oliveira_, Apr 04 2025: (Start) %F A139264 G.f.: 7*x*(1+9*x)/(1-x)^2. %F A139264 E.g.f.: 7*(exp(x)*(10*x - 9) + 9). %F A139264 a(n) = 7*A017281(n-1). %F A139264 a(n) = 2*a(n-1) - a(n-2) for n > 2. (End) %t A139264 70*Range[50]-63 (* _Harvey P. Dale_, May 06 2019 *) %o A139264 (Magma) [70*n-63: n in [1..50]]; // _Vincenzo Librandi_, Jun 19 2011 %o A139264 (PARI) a(n)=70*n-63 \\ _Charles R Greathouse IV_, Aug 25 2014 %Y A139264 Subsequence of A034709, together with A017281, A017293, A139222, A139245, A017329, A139249, A139279 and A139280. %K A139264 easy,nonn %O A139264 1,1 %A A139264 _Odimar Fabeny_, Jun 06 2008 %E A139264 More terms from _Reinhard Zumkeller_, Jun 22 2008