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 A134154 #16 Jun 08 2025 03:34:11
%S A134154 1,7,43,109,205,331,487,673,889,1135,1411,1717,2053,2419,2815,3241,
%T A134154 3697,4183,4699,5245,5821,6427,7063,7729,8425,9151,9907,10693,11509,
%U A134154 12355,13231,14137,15073,16039,17035,18061,19117,20203,21319,22465,23641
%N A134154 a(n) = 15*n^2 - 9*n + 1.
%C A134154 A119617 is union of A134153 and A134154 A000538(n) is divisible by A000330(n) if and only n is congruent to {1, 3} mod 5 (see A047219) A134154(n) is case when n is congruent to 3 mod 5 see cases 2)
%H A134154 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A134154 a(n) = 15*n^2 - 9*n + 1.
%F A134154 a(n+1) = (3*(5*n + 3)^2 + 3*(5*n + 3) - 1)/5.
%F A134154 a(n+1) = (Sum_{k=1..5*n+3} k^4) / (Sum_{k=1..5*n+3} k^2).
%F A134154 G.f.: -(1+4*x+25*x^2)/(-1+x)^3. - _R. J. Mathar_, Nov 14 2007
%t A134154 Table[1 - 9 n + 15 n^2, {n, 0, 50}]
%t A134154 Table[Sum[k^4, {k, 1, 5m + 3}]/Sum[k^2, {k, 1, 5m + 3}], {m, 0, 30}]
%o A134154 (PARI) a(n)=15*n^2-9*n+1 \\ _Charles R Greathouse IV_, Jun 17 2017
%Y A134154 Cf. A000538, A119617, A134153.
%K A134154 nonn,easy
%O A134154 0,2
%A A134154 _Artur Jasinski_, Oct 10 2007