Heehaww makes a very good point! Let me see if I am following. Remaining cards can be anything: 47 other cards of which 2 go to player and 2 go to board. So we need to divvy up one of the 40 possible straight flushes so that 2 of the 5 cards get dealt to player and the other 3 appear on the board. Straight flush: any of 40 five-card combinations when suits are taken into account (including royal flushes - clearly if royal flushes are to be excluded, change the 40 below to 36).
Omaha: use exactly two cards from your hand of four cards + use three cards from a community board of five cards (I apologize in advance if anyone takes offense to my posting in this nature.) Once the real experts in this field post the correct answer, I can learn how to improve my thinking on these types of questions. But I readily admit that this type of calculation is not my strong suit and the answer below could well be wrong.
