909091

Properties

Appears in sequences

• Irregular table read by rows: row n lists prime factors of 10^n + 1, with multiplicity.at n=13A001271
• Largest prime factor of the "repunit" number 11...1 (cf. A002275).at n=12A003020
• Largest prime factor of 10^n + 1.at n=7A003021
• Largest prime factor of 10^n + 1.at n=21A003021
• Largest prime factor of 10^n - 1.at n=13A005422
• Smallest primitive factor of 10^n - 1. Also smallest prime p such that 1/p has repeating decimal expansion of period n.at n=13A007138
• Primes with unique period length (the periods are given in A007498).at n=7A007615
• a(n) = (1 - (-10)^n)/11.at n=6A014992
• Triangle of q-binomial coefficients for q=-10.at n=34A015123
• Triangle of q-binomial coefficients for q=-10.at n=29A015123
• Gaussian binomial coefficient [ n,6 ] for q = -10.at n=1A015333
• a(n) = 9*a(n-1) + 10*a(n-2).at n=7A015585
• Cyclotomic polynomials at x=10.at n=13A019328
• Cyclotomic polynomials at x=-10.at n=7A020509
• Prime 3 followed by unique period primes (the period r of 1/p is not shared with any other prime) of the form A019328(r)/gcd(A019328(r),r) in order (periods r are given in A051627).at n=7A040017
• Triangle of prime numbers in which n-th row lists all primes p such that 1/p has decimal period n, n >= 1.at n=20A046107
• Primes whose consecutive digits differ by 8 or 9.at n=13A048420
• a(n) = n^6 - n^5 + n^4 - n^3 + n^2 - n + 1.at n=10A060888
• Greatest prime number p(n) with decimal fraction period of length n.at n=13A061075
• a(n) = A083147(n+1)/A083147(n).at n=16A083148