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 A154105 #42 Sep 13 2022 13:05:30 %S A154105 7,37,91,169,271,397,547,721,919,1141,1387,1657,1951,2269,2611,2977, %T A154105 3367,3781,4219,4681,5167,5677,6211,6769,7351,7957,8587,9241,9919, %U A154105 10621,11347,12097,12871,13669,14491,15337,16207,17101,18019,18961,19927,20917,21931 %N A154105 a(n) = 12*n^2 + 18*n + 7. %C A154105 a(n) is the number of partitions with three integral dissimilar components of the number 12(n+1), e.g for n=0, 12 may be partitioned in the 7 ways (1,2,9), (1,3,8), (1,4,7), (1,5,6), (2,3,7), (2,4,6) and (3,4,5). - _Ian Duff_, Jan 31 2010 %C A154105 Sequence found by reading the line from 7, in the direction 7, 37, ..., in the square spiral whose vertices are the generalized octagonal numbers A001082. - _Omar E. Pol_, May 08 2018 %H A154105 Vincenzo Librandi, <a href="/A154105/b154105.txt">Table of n, a(n) for n = 0..3000</a> %H A154105 John Elias, <a href="/A154105/a154105.gif">Animated Illustration: Starburst Hexagrams</a> %H A154105 Leo Tavares, <a href="/A154105/a154105.jpg">Illustration: Hexagonal Halos</a> %H A154105 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1). %F A154105 G.f.: (7 + 16*x + x^2)/(1-x)^3. %F A154105 a(n) = 6*A014106(n) + 7. %F A154105 a(0) = 7; for n > 0, a(n) = a(n-1) + 24*n + 6. %F A154105 a(-n-1) = 2*A085473(n) - 1. - _Bruno Berselli_, Sep 05 2011 %F A154105 E.g.f.: (7 + 30*x + 12*x^2)*exp(x). - _G. C. Greubel_, Sep 02 2016 %F A154105 a(n) = 1 + A152746(n+1). - _Omar E. Pol_, May 08 2018 %F A154105 a(n) = A003215(n) + 6*A000290(n+1) + 6*A000217(n). - _Leo Tavares_, Sep 12 2022 %e A154105 a(2) = 12*2^2 + 18*2 + 7 = 91 = 6*14 + 7 = 6*A014106(2) + 7. %e A154105 a(3) = a(2) + 24*3 + 6 = 91 + 72 + 6 = 169. %e A154105 a(-4) = 12*4^2 - 18*4 + 7 = 127 = 2*64 - 1 = 2*A085473(3) - 1. %t A154105 Table[12*n^2 + 18*n + 7, {n, 0, 42}] (* _Vladimir Joseph Stephan Orlovsky_, Feb 20 2012 *) %t A154105 LinearRecurrence[{3,-3,1}, {7,37,91}, 25] (* _G. C. Greubel_, Sep 02 2016 *) %o A154105 (Magma) [ 12*n^2+18*n+7: n in [0..40] ]; %o A154105 (PARI) a(n)=12*n^2+18*n+7 \\ _Charles R Greathouse IV_, Sep 02 2016 %Y A154105 Cf. A001082, A014106, A152746, A153286, A085473. %Y A154105 Cf. A003215, A000290, A000217. %K A154105 nonn,easy %O A154105 0,1 %A A154105 _Klaus Brockhaus_, Jan 04 2009