MathCastle
AIMEChallengeAdvanced Number Theory

Advanced Number Theory · Challenge problem

Find the number of integers nn with 1≤n≤15001 \le n \le 1500 such that n≡4(mod9)n \equiv 4 \pmod{9} and gcd⁡(n,10)=1\gcd(n, 10) = 1.