18 43 56 115 136 170 | The death of Roberto Clemente, December 31, 1972, in a 'plane crash'

Robert Clemente was delivering aid to Puerto Rico when his plane crashed and killed him on New Year's Eve, 1972.

12/31 = 12+31 = 43 
(Masonic = 43) (Killing = 43) (RIP = 43) (Plane Crash = 43) (Pirates = 43)

Further...

12/31/72 = 12+31+72 = 115
(Killing = 115) (Masonic = 115)

He died on his 136th day of his age.

136, the 16th triangular number
P = 16 (P is the symbol for the Pittsburgh Pirates)

He has played 18-seasons.

He died 135-days after his birthday, or a span of 136-days.

136-days is also 19-weeks and 3-days.

193, the 44th prime; Kill = 44; Execution = 44

Roberto Clemente = 170; Sacrifice = 170

Pittsburgh Pirates = 228 (Ordinal)

Death = 228 (Sumerian)