Unusual number sequences

(1)

0

1+2=3

4+5+6=7+8

9+10+11+12=13+14+15

16+17+18+19+20=21+22+23+24

25+26+27+28+29+30=31+32+33+34+35

36+37+38+39+40+41+42=43+44+45+46+47+48

49+50+51+52+53+54+55+56=57+58+59+60+61+62+63

64+65+66+67+68+69+70+71+72=73+74+75+76+77+78+79+80

81+82+83+84+85+86+87+88+89+90=91+92+93+94+95+96+97+98+99

.....................................................................................................................................

etc.