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 A213907 #8 Dec 16 2024 14:35:54
%S A213907 1,3,9,34,61,261,709,1324,4937,15040,28561,107262,248341,522445,
%T A213907 1972363,7591936,8835345,26421129,145475533,183752250,701184621,
%U A213907 2234736295,2996725227,15105451596,32483720761,77618520551,217809217211,625456400842,1638545943301
%N A213907 a(n) = 1 + n + n*{n/2} + n*{n/2}*{n/3} + n*{n/2}*{n/3}*{n/4} +... where {x} = [x+1/2] = round(x).
%e A213907 a(2) = 1 + 2 + 2*1 + 2*1*1 + 2*1*1*1 = 9.
%e A213907 a(3) = 1 + 3 + 3*2 + 3*2*1 + 3*2*1*1 + 3*2*1*1*1 + 3*2*1*1*1*1 = 34.
%o A213907 (PARI) {a(n)=1+sum(m=1, 2*n, prod(k=1, m, round(n/k)))}
%o A213907 for(n=0, 60, print1(a(n), ", "))
%Y A213907 Cf. A075885.
%K A213907 nonn
%O A213907 0,2
%A A213907 _Paul D. Hanna_, Jun 24 2012