cp's OEIS Frontend

A274091 Take alternate terms of A274088 and A274090.

%I A274091 #21 Jun 20 2016 19:36:44
%S A274091 0,0,1,1,4,1,9,-1,15,-7,20,-15,23,-28,23,-43,20,-61,11,-80,-2,-100,
%T A274091 -21,-119,-46,-137,-76,-151,-111,-162,-150,-167,-194,-167,-240,-161,
%U A274091 -289,-147,-339,-125,-389,-95,-437,-57,-484,-11,-527,44,-566,107,-599,177,-626,255,-645,339,-656,429,-658,524
%N A274091 Take alternate terms of A274088 and A274090.
%H A274091 N. J. A. Sloane and Chai Wah Wu, <a href="/A274091/b274091.txt">Table of n, a(n) for n = 0..10000</a> n = 0..1000 from N. J. A. Sloane.
%p A274091 Digits:=50:
%p A274091 f:=n->round(evalf(n^2*sin(sqrt(n)))); # A274088
%p A274091 fc:=n->round(evalf(n^2*cos(sqrt(n)))); # A274090
%p A274091 fu:=n->if n mod 2 = 0 then f(n/2) else fc((n-1)/2); fi;
%p A274091 [seq(fu(n),n=0..120)];
%o A274091 (Python)
%o A274091 from sympy import sin, sqrt, pi
%o A274091 def f(n, t = 1):
%o A274091     k, j = divmod(n,t)
%o A274091     return int((k**2*sin(sqrt(k)+j*pi/2)).round())
%o A274091 A274091_list = [f(n,2) for n in range(10001)] # _Chai Wah Wu_, Jun 11 2016
%Y A274091 Sequences of the same type: A272695, A274086, A274087, A274088, A274090, A274091, A274092, A274095, A274096, A274097, A274101, A274102.
%Y A274091 See A274092 for a three-strand version.
%K A274091 sign
%O A274091 0,5
%A A274091 _N. J. A. Sloane_, Jun 10 2016