Introductio in analysin infinitorum

268 DE PARTITIONE LIB. I. $1+1+2+3+4+5+7+8+10+12+14+16+19$ &c. $1+2+4+6+9+12+16+20+25+30+36+42+49$ &c. $1+3+6+10+15+21+28+36+45+55+66+78+91$ &c. Vicissim autem apparet quomodo ex Serie trigonalium erui debeat Series superior. 321. Simili modo, quia Series quarta oritur ex fractione $\frac{1}{(1-x)(1-xx)(1-x^3)(1-x^4)}$, erit $\frac{(1+x)(1+x+xx)(1+x+xx+x^3)}{(1-x)(1-xx)(1-x^3)(1-x^4)} = \frac{1}{(1-x)^4}$. Si in Serie quarta primum quaterni termini addantur, tum in Serie resultante terni, denique in hac bini, prodibit Series numerorum pyramidalium uti ex sequenti calculo videre licet. $1+1+2+3+5+6+9+11+15+18+23+ [TRUNCATED]