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 A101473 #16 Jun 11 2022 20:06:18 %S A101473 0,1,3,9,31,111,453,2059,10571,60651,386253,2704659,20661411, %T A101473 170990691,1523975053,14552848059,148234015051,1604267622731, %U A101473 18383552327853,222363321668259,2831217743661491,37850593064646771,530121590756400653 %N A101473 Boustrophedon transform of the Jacobsthal numbers. %C A101473 Binomial transform of A101474. %F A101473 E.g.f.: (sec(x) + tan(x))*(exp(2*x) - exp(-x))/3. %F A101473 a(n) = (A000752(n) - A062162(n))/3. %F A101473 a(n) ~ n! * 2^(n+2) * (exp(Pi) - exp(-Pi/2)) / (3 * Pi^(n+1)). - _Vaclav Kotesovec_, Jun 12 2015 %o A101473 (Python) %o A101473 from itertools import accumulate, islice %o A101473 def A101473_gen(): # generator of terms %o A101473 blist, a, b = tuple(), 0, 1 %o A101473 while True: %o A101473 yield (blist := tuple(accumulate(reversed(blist),initial=a)))[-1] %o A101473 a, b = b, 2*a+b %o A101473 A101473_list = list(islice(A101473_gen(),30)) # _Chai Wah Wu_, Jun 11 2022 %Y A101473 Cf. A000752, A001045, A062162, A101474. %K A101473 easy,nonn %O A101473 0,3 %A A101473 _Paul Barry_, Jan 21 2005