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Mentioned in Paus. 6.3.11, where it is said he was a runner who won five times at Pytho (Delphi), three times in the Isthmian games, four at Nemea, three times at Olympia (one boys' and two mens' victories); it is also said he was originally from Kaulonia but later in his career proclaimed ('was bribed to') to be from Syrakousai. This is e.g. visible in Anth. Gr. 13.15, which mentions one less Olympian victory. For the dating I follow Farrington (2012), no. 1.60 and p. 120 note 279 - partly based on Moretti (1957), nos. 379 and 388-9 who placed the first Olympian victory in 392 B.C. and the other two in 384 B.C. - PK
Dikon won five races at the Pythia, three at the Isthmia, four at the Nemea. He won one boys' stadion-race and two men's races at the Olympia. He was from Kaulonia, but in the final two victories he was bribed to proclaim himself as Syracusan, according to Pausanias. Moretti, however, claims the Kaulonians were transferred to Syracuse in 389 BC.
The first victory in the boys' running match should have been before 389 BC. Moretti 1957, no. 379 suggests the 97th Olympiad (= 396 BC), The third victory may have been at the same Olympiad as his stadion-victory (for instance in diaulos or hoplite), but it could have been at another Olympiad as well. - DL