(e^(iπ/2))^n=cos(nπ/2)+isin(nπ/2)=i^n
n=∫(0→2) i^n=4i/π≒(1+1/(3+4/(5+9/(7+16/(9+25/(11+36/(13+49/(15+64/(17+81/(19+100/(21+121/(23+144/(25+169/(27+196/(29+225/(31+256/(33+289/35)))))))))))))))))i