is 3 on a and 2 han after a call. The number tiles are one suit, and the hand includes honors.
The name players use is honitsu (混一色). This site's glossary also lists it as Half Flush. Players also call it a half flush.
One suit, plus honors
Every numbered tile shares a suit. Winds, dragons, or both make up the rest. A second suit removes the yaku. A hand with no honors is chinitsu: 6 han closed and 5 han open.
The number tiles are . The honors are a triplet of west and a pair of red dragons. The hand waits on or . Either tile keeps the one suit and the honors.
A west triplet is yakuhai when you are West or the round is West. A red-dragon triplet is in every seat. When that triplet is yakuhai, add its han. Honitsu itself is 3 han closed, or 2 han open.
Closed or open
The EMA 2016 list files half flush with the 2 han yaku, and adds one han when the hand is concealed. That is the same pair of numbers as the row on this site: 3 closed, 2 open. A , a , or an is the open case.
The glossary entry is the short form: one suit plus honors, 3 han closed and 2 han open.
What 2 han 30 fu pays
An open honitsu with no extra fu is 20 fu, and that rounds up to 30. At 2 han 30 fu, a collects 2,000. The dealer collects 2,900. Those payments have no and no sticks.
A closed hand is 3 han from this yaku before and before any other yaku. A tsumo on a closed hand also has menzen tsumo.
Price a honitsu hand
The score calculator turns 2 han 30 fu, an open honitsu with no extra fu, into 2,000 or 2,900. A closed hand starts at 3 han.
Open the score calculator