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 A381757 #9 Mar 06 2025 08:28:03
%S A381757 1,6,161,6062,265868,12720904,643915209,33905228350,1838102210977,
%T A381757 101910583801012,5751779249830131,329359930638541776,
%U A381757 19087504000780665541,1117418973753045781944,65982722733895652916539,3925378032146863676341770,235048328495265879957413946
%N A381757 Expansion of exp( Sum_{k>=1} binomial(7*k-1,2*k-1) * x^k/k ).
%F A381757 a(0) = 1; a(n) = (1/n) * Sum_{k=1..n} binomial(7*k-1,2*k-1) * a(n-k).
%F A381757 G.f.: B(x)^2, where B(x) is the g.f. of A300386.
%o A381757 (PARI) my(N=20, x='x+O('x^N)); Vec(exp(sum(k=1, N, binomial(7*k-1, 2*k-1)*x^k/k)))
%Y A381757 Cf. A006013, A079489, A182960, A381751, A381752, A381753, A381758.
%Y A381757 Cf. A300386.
%K A381757 nonn,easy
%O A381757 0,2
%A A381757 _Seiichi Manyama_, Mar 06 2025