27397

Properties

Appears in sequences

• Numbers k such that lcm(1,2,3,...,k)/13 equals the denominator of the k-th harmonic number H(k).at n=23A112818
• Primes of the form p = prime(k) = (prime(k+3)+prime(k-1))/2.at n=27A126238
• Prime numbers p for which the quintic polynomial x^5 - x - 1 modulo p completely factors into linear polynomials.at n=20A135844
• Prime numbers p not of the form 10*k+1 for which the quintic polynomial x^5-x-1 modulus p is factorizable into five binomials.at n=15A135845
• Prime p1 of consecutive primes p1, p2, where p2-p1=10, and p1, p2 are in different centuries.at n=29A160500
• Row sums of triangle A178568.at n=24A169826
• Number of (n+1) X (n+1) -2..2 symmetric matrices with every 2 X 2 subblock having sum zero and one, two or three distinct values.at n=9A211116
• Primes that remain prime when a single digit 9 is inserted between any two consecutive digits or as the leading or trailing digit.at n=25A215421
• Primes p such that 10p + 1, 100p + 1 and 1000p + 1 are also primes.at n=28A243962
• Primes p whose last digit is the same as that of both its predecessor prime and its successor prime.at n=26A298075
• Left-truncatable happy numbers: every suffix is a happy number and no digits are zero.at n=21A383639
• Prime numbersat n=2994