Hello,
NITs like NIT WRANGAL,SURATHKAL,DURGAPUR,MANIPUR,PATNA,ARUNANCHAL PRADESH offers Mathematics and Computing Btech course in their respective colleges.For details about this you can visit the below given link :
https://engineering.careers360.com/colleges/list-of-mathematics-and-computing-engineering-colleges-in-india
Good luck.

1.IIT Kgp
2. IIT Patna
3. MANIT Bhopal
4. NIT Patna
5. IIT Madras

refer this link:

https://www.careers360.com/mathematics-and-computing-engineering-course

NITs like Durgapur, Warangal and Suratkal and Nanipur offer Btech in Mathematics and Computing engineering specialization.

There are some ither few good college as well which offer such courses as given below.

https://engineering.careers360.com/colleges/list-of-mathematics-and-computing-engineering-colleges-in-india
Course entaiks integration of mathematics and statistics in computer applications.