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 A231895 #17 Jun 15 2022 01:49:48 %S A231895 3,3,5,12,37,138,605,3042,17257,108978,758105,5759322,47439277, %T A231895 421090218,4006875605,40686781602,439122198097,5019624693858, %U A231895 60582649901105,769831261587882,10273367294485717,143649246839399898,2100196647406842605,32044492213621026162,509357494543973054137 %N A231895 a(n) = 2*A000111(n+1) + A000111(n). %C A231895 It is clear from the Berry et al. article that they intended to consider 2*A000111(n+1) - A000111(n) (which is A104854), not 2*A000111(n+1) + A000111(n). %H A231895 D. Berry, J. Broom, D. Dixon, and A. Flaherty, <a href="https://www.math.lsu.edu/system/files/DeAngelisProject2.pdf">Umbral Calculus and the Boustrophedon Transform</a>, 2013. %F A231895 E.g.f.: 1 + (sec(x) + tan(x) + 1)*(sec(x) + tan(x)). - _Sergei N. Gladkovskii_, Jun 11 2015 %o A231895 (Python) %o A231895 from itertools import accumulate, islice %o A231895 def A231895_gen(): # generator of terms %o A231895 yield 3 %o A231895 blist = (0,1) %o A231895 while True: %o A231895 yield blist[-1]+2*(blist := tuple(accumulate(reversed(blist),initial=0)))[-1] %o A231895 A231895_list = list(islice(A231895_gen(),40)) # _Chai Wah Wu_, Jun 14 2022 %Y A231895 Cf. A000111, A104854. %K A231895 nonn %O A231895 0,1 %A A231895 _N. J. A. Sloane_, Nov 18 2013