a tetrahedron is what you call for a pyramid with a triangular base.
a tetrahedron is what you call for a pyramid with a triangular base.
what do you call a pyramid with a triangular base?
a tetrahedron
tetrahedral number









































a tetrahedral number, or triangular pyramidal number, is a figurate number that represents a pyramid with a triangular base and three sides, called a tetrahedron. the "n"-th tetrahedral number, formula_1, is the sum of the first "n" triangular numbers, that is, formula_2









































the tetrahedral numbers are:









































section::::formula.









































the formula for the "n"-th tetrahedral number is represented by the 3rd rising factorial of "n" divided by the factorial of 3:









































the tetrahedral numbers can also be represented as binomial coefficients:









































tetrahedral numbers can therefore be found in the fourth position either from left or right in pascal's triangle.
tetrahedral number
in contrast to the figurative art which had characterized it earlier, from the 1950s on a growing tendency towards abstraction began to appear in memorial sculpture. at the center of the “pilots’ memorial" (1950s), erected by benjamin tammuz and aba elhanani in the independence park in tel aviv-yaffo, stands an image of a bird flying above a tel aviv seaside cliff. the tendency toward the abstract can also be seen the work by david palombo, who created reliefs and memorial sculptures for government institutions like the knesset and yad vashem, and in many other works, such as the memorial to shlomo ben-yosef that itzhak danziger erected in rosh pina. however, the epitome of this trend toward avoidance of figurative images stands our starkly in the “monument to the negev brigade” (1963–1968) which dani karavan created on the outskirts of the city of beersheva. the monument was planned as a structure made of exposed concrete occasionally adorned with elements of metaphorical significance. the structure was an attempt to create a physical connection between itself and the desert landscape in which it stands, a connection conceptualized in the way the visitor wanders and views the landscape from within the structure. a mixture of symbolism and abstraction can be found in the “monument to the holocaust and national revival”, erected in tel aviv’s rabin square (then “kings of israel square”). igael tumarkin, creator of the sculpture, used elements that created the symbolic form of an inverted pyramid made of metal, concrete, and glass. in spite of the fact that the glass is supposed to reflect what is happening in this urban space, the monument didn’t express the desire for the creation of a new space which would carry on a dialogue with the landscape of the “land of israel”. the pyramid sits on a triangular base, painted yellow, reminiscent of the “mark of cain”. the two structures together form a magen david. tumarkin saw in this form “a prison cell that has been opened and breached. an overturned pyramid, which contains within itself, imprisoned in its base, the confined and the burdensome.” the form of the pyramid shows up in another work of the artists as well. in a late interview with him, tumarkin confided that the pyramid can be perceived also as the gap between ideology and its enslaved results: “what have we learned since the great pyramids were built 4200 years ago?[...] do works of forced labor and death liberate?”
israeli sculpture