geometrical pattern of four conjoined spirals, a tetraskelion or tetraskele

spiral quadruple fourfold spirals tetraskelion tetraskele four symbol motif pattern conjoined celtic ancient twoarmed doublearmed sign seamless endless loopable connected symmetry geometry sacred archimedean rotational vortex swirl twist curl line double arm neolithic arithmetic linear windings circular radial concentric circularly shape rotating turnings round black isolated vector