54 VE ARITHMETICA nCVRATA 



nim ferieriim ordine continentiir omnes polygoni 

 mimeri : In quarto pyramidiilcs primi , in qiiinto 

 pyramidales lccundi , et fic deinceps : Ergo tota 

 haec flimilia generali formula exhibctur (§>. 9.) quae 

 fequitur. 



• i 2 • ^ n ^ -^ ' 



; — i 3c-f-n — 2 



\'bi .r radicem fiue latusnumeri figurati fignificat,et, 

 in indicem ordinis ad qucm figuratus numerus pcr- 

 tinet. 



41. In fpecie , quia Polygoni pertinent ad 

 ordinem tertium (§. 48.) crit eorum fo-rmula znrt^. 

 -(i-^)^. Pyramidalcs primi erunt confcquen- 



ic-)-l 



ter r/^.^^=tiL.-:^±Ll.-i-(i-fl)^.?rtL, Pyramidales fecun 

 di — tf?-.^.fit2.^=bi_f- (i^^) ^.5±ii =^±2.: Et fic 



porro. 



42. Qiiod fi flat ^Tzni. tumvocantur hi nume- 

 ri triangulares, fi r/zr^ , vocantur quadrangulares, 

 et in genere , fi numerui) angulorum fit -zzzp ciii azzi 

 p-2. hoc crgo valore fubllitutoin formuhi figurato- 

 rum gcnerah (§. 48.) fiet illa — (p-2)^.^±i. ^^-^ 



43. Numeri trianguhires formula exprimun- 

 tur omnium fimphcilhma , pofito enim />— 3 Iia- 

 bebitur omnium triangularium cxprQffio—^.^^^. 

 2±il.^y:ii . . ~^^. Iii fpecie autem pofito «^13 

 erunt polygoni triangulares m^^.^iti. pofito a~^ 

 erunt triangulares pyramidales primi — ^.Erhl.^dbi, 

 Et fic deinceps. Colhitis his exprefhonibus cum 



coef- 



