Brihat Jataka
द्वित्रिचतुर्दशदशतिथिसप्तत्रिगुणा नवाष्ट चैन्द्राद्या: ॥ पञ्चदशघ्नास्तद्दिङ्मुखान्विता भं घनिष्ठादि ॥ २६-१६ ॥
The numbers are 2, 3, 14, 10, 15, 21, 9, and 8 beginning with the regent of the east quarter, etc. That number is multiplied by 15 ॥ and added to the number॥ of those gathered facing that direction. ॥ Divided by 27 will give the nakshatra॥ beginning with the nakshatra of Dhanishtha.
english translation
dvitricaturdazadazatithisaptatriguNA navASTa caindrAdyA: ॥ paJcadazaghnAstaddiGmukhAnvitA bhaM ghaniSThAdi ॥ 26-16 ॥
hk transliteration by Sanscript