A274091 Take alternate terms of A274088 and A274090.

0, 0, 1, 1, 4, 1, 9, -1, 15, -7, 20, -15, 23, -28, 23, -43, 20, -61, 11, -80, -2, -100, -21, -119, -46, -137, -76, -151, -111, -162, -150, -167, -194, -167, -240, -161, -289, -147, -339, -125, -389, -95, -437, -57, -484, -11, -527, 44, -566, 107, -599, 177, -626, 255, -645, 339, -656, 429, -658, 524

Offset: 0

Author

N. J. A. Sloane, Jun 10 2016

Keywords

• sign

Links

• N. J. A. Sloane and Chai Wah Wu, Table of n, a(n) for n = 0..10000 n = 0..1000 from N. J. A. Sloane.

Crossrefs

Sequences of the same type: A272695, A274086, A274087, A274088, A274090, A274091, A274092, A274095, A274096, A274097, A274101, A274102.

See A274092 for a three-strand version.

Programs

Maple

Digits:=50:
f:=n->round(evalf(n^2*sin(sqrt(n)))); # A274088
fc:=n->round(evalf(n^2*cos(sqrt(n)))); # A274090
fu:=n->if n mod 2 = 0 then f(n/2) else fc((n-1)/2); fi;
[seq(fu(n),n=0..120)];

Python

from sympy import sin, sqrt, pi
def f(n, t = 1):
    k, j = divmod(n,t)
    return int((k**2*sin(sqrt(k)+j*pi/2)).round())
A274091_list = [f(n,2) for n in range(10001)] # Chai Wah Wu, Jun 11 2016