One of the 24 7-polyiamonds.
Heptiamond
See also
Heptiamond Tiling, PolyiamondExplore with Wolfram|Alpha
References
Gardner, M. The Sixth Book of Mathematical Games from Scientific American. Chicago, IL: University of Chicago Press, pp. 246, 248, and 250-251, 1984.Referenced on Wolfram|Alpha
HeptiamondCite this as:
Weisstein, Eric W. "Heptiamond." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Heptiamond.html