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 A101474 #9 Jun 11 2022 16:41:13 %S A101474 0,1,1,3,9,21,111,393,2309,12321,81071,560033,4301109,35526921, %T A101474 316858231,3025055673,30815437909,333492212321,3821573586591, %U A101474 46224758487313,588552491006709,7868364598774521,110201454736846151,1613597716238974953,24653957361927031509 %N A101474 Boustrophedon transform of the signed Jacobsthal numbers. %C A101474 Boustrophedon transform of (-1)^n*A001045(n). Binomial transform is A101473. %F A101474 E.g.f.: (sec(x)+tan(x))*(exp(x)-exp(-2*x))/3. %F A101474 a(n) ~ n! * (exp(3*Pi/2)-1) * 2^(n+2) / (3 * exp(Pi) * Pi^(n+1)). - _Vaclav Kotesovec_, Jun 12 2015 %o A101474 (Python) %o A101474 from itertools import accumulate, islice %o A101474 def A101474_gen(): # generator of terms %o A101474 blist, a, b = tuple(), 0, -1 %o A101474 while True: %o A101474 yield (blist := tuple(accumulate(reversed(blist),initial=a)))[-1] %o A101474 a, b = -b, -2*a-b %o A101474 A101474_list = list(islice(A101474_gen(),30)) # _Chai Wah Wu_, Jun 11 2022 %Y A101474 Cf. A001045. %K A101474 easy,nonn %O A101474 0,4 %A A101474 _Paul Barry_, Jan 21 2005