21821

Properties

Appears in sequences

• Largest prime dividing sigma(5,n).at n=29A078554
• Theorems from propositional calculus, translated into decimal digits.at n=35A101273
• Prime(144*n).at n=16A102350
• Column 6 of triangle A117418.at n=6A117424
• Triangle T, read by rows, formed by a column bisection of triangle A117418: column k of T equals column 2*k of A117418.at n=48A117425
• Expansion of 1/(1-x-x^2+x^3-x^4).at n=25A124280
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (-1, 1, 0), (0, 1, -1), (0, 1, 1), (1, -1, 0)}.at n=9A148882
• Primes of the form XYX, where Y is a single digit.at n=31A154270
• Primes of the form 2n^2+14n+5.at n=18A154577
• Primes p such that p^2 + 6, p^2 + 12 and p^2 + 18 are all prime.at n=11A173627
• a(n)=(F(n)-sumofdigits(F(n)))/9, where F(n) = A000045(n).at n=27A181065
• Smaller of the two consecutive primes whose sum is a triangular number.at n=31A225077
• Primes of the form abcabc..abcab.at n=16A228627
• Greatest prime factor of n^5 + 1.at n=30A240548
• Primitive prime factors of the cyclotomic polynomial sequence Phi(10,k) in the order in which they occur.at n=31A248874
• Smallest primes of 3 X 3 semimagic squares formed from consecutive primes.at n=0A265139
• A set of nine consecutive primes forming a 3 X 3 semimagic square with the smallest magic constant (65573).at n=0A265614
• Smallest of n^2 consecutive primes that form an n X n semimagic square with the least magic sum, or 0 if no such magic square exists.at n=2A270830
• a(n) = smallest prime q such that Sum_{primes p <= q} 1/sqrt(p) >= n.at n=38A292775
• Number of rooted twice-partitions of n where the composite rooted partition is strict.at n=29A301750