何なんだよ	35713

There's a million common expressions you can make like this. I don't think we need the majority of them.

https://www.quora.com/What-does-the-phrase-Nanda-Yo-mean-in-Japanese

I'm a bit confused by all the possible forms and how to pontenially combine them in the dictionary. 'nanda' is in the dictionary', but perhaps 'nandayo' is common enough for its own entry? nannandayo seems to make the expression even stronger. there's also 'っだよ' which according to my native friend has a similar meaning, but perhaps that's too conversational for the dictionary.

n-gram counts:

なんだよ	      5990999
何だよ	       192471
なんなんだよ	56601
何なんだよ	35713
っだよ	         2331