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 A218330 #7 Aug 01 2015 10:38:44
%S A218330 1,11,175,301,1005,1375,3003,3745,6681,7923,12551,14421,21125,23751,
%T A218330 32915,36425,48433,52955,68191,73853,92701,99631,122475,130801,158025,
%U A218330 167875,199863,211365,248501,261783,304451,319641,368225,385451,440335,459725,521293
%N A218330 Odd decagonal pyramidal numbers.
%H A218330 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1, 3, -3, -3, 3, 1, -1).
%F A218330 a(n) = a(n-1) + 3*a(n-2) - 3*a(n-3) - 3*a(n-4) + 3*a(n-5) + a(n-6) - a(n-7).
%F A218330 a(n) = 3*a(n-2) - 3*a(n-4) + a(n-6) + 512.
%F A218330 a(n) = (16*n-4*(-1)^n-17)*(4*n-(-1)^n-3)*(4*n-(-1)^n-1)/24.
%F A218330 G. f. x*(1+10*x+161*x^2+96*x^3+215*x^4+22*x^5+7*x^6)/((1-x)^4*(1+x)^3).
%e A218330 The sequence of decagonal pyramidal numbers A007585 begins 0, 1, 11, 38, 90, 175, 301, 476, 708, 1005, 1375,... As the third odd term is 175, then a(3) = 175.
%t A218330 LinearRecurrence[{1,3,-3,-3,3,1,-1}, {1,11,175,301,1005,1375,3003}, 37]
%Y A218330 Cf. A007585, A218331.
%K A218330 nonn
%O A218330 1,2
%A A218330 _Ant King_, Oct 29 2012