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 A386272 #12 Jul 20 2025 14:40:04
%S A386272 1,21,735,29155,1224510,53143734,2356038874,106021749330,
%T A386272 4823989594515,221367522503855,10227179539678101,475098976797773601,
%U A386272 22171285583896101380,1038639455430209672340,48816054405219854599980,2300863364299362480145724,108715793963144877186885459
%N A386272 Expansion of 1/(1 - 49*x)^(3/7).
%F A386272 a(n) = (-49)^n * binomial(-3/7,n).
%F A386272 a(n) = 7^n/n! * Product_{k=0..n-1} (7*k+3).
%F A386272 a(n) = 7^n * Product_{k=1..n} (7 - 4/k).
%F A386272 D-finite with recurrence n*a(n) +7*(-7*n+4)*a(n-1)=0. - _R. J. Mathar_, Jul 20 2025
%o A386272 (PARI) my(N=20, x='x+O('x^N)); Vec(1/(1-49*x)^(3/7))
%Y A386272 Cf. A034835, A216703, A386271, A386273, A386274.
%Y A386272 Cf. A049381, A216702.
%K A386272 nonn,easy
%O A386272 0,2
%A A386272 _Seiichi Manyama_, Jul 17 2025