90089

Properties

Appears in sequences

• Primes starting and ending with 9.at n=31A062335
• Table read by rows where i-th row consists of primes P of the form P=j*P(i)# -1 or P=j*P(i)# +1 with 0 < j < P(i+1). Here P(r)# = A002110.at n=44A087715
• Emirps starting and ending with composite digit 9.at n=10A128374
• Smallest emirp corresponding to the prime of A178583.at n=21A178584
• The smaller member prime(i) of an emirp pair (prime(i),prime(j)), such that the digit sum of i equals the digit sum of j.at n=31A178613
• Sophie Germain primes that are also highly cototient numbers.at n=20A209194
• Primes of the form n^3 - T(n) - 1 where T(n) is the n-th triangular number.at n=11A229960
• Primes of the form A060735(k) +- 1, where A060735 lists multiples of primorials (A002110) less than the next larger primorial.at n=43A257658
• Numbers k such that phi(sigma(k))/k < phi(sigma(m))/m for all m < k, where sigma is the sum of divisors function (A000203) and phi is Euler's totient function (A000010).at n=30A293711
• Numbers k such that phi(psi(k))/k < phi(psi(m))/m for all m < k, where phi is Euler's totient function (A000010) and psi is the Dedekind psi function (A001615).at n=32A293713
• Numbers k where records occur for phi(k)/phi(k+1), where phi is the Euler totient function (A000010).at n=26A335070
• a(n) is the least number whose sum of digits in primorial base equals n.at n=37A343048
• Numbers k such that (100^k + 1)/101 is prime.at n=4A347138
• Triple convolution of the three tribonacci-like sequences A000073(n), A077947(n-2), and A103143(n).at n=18A373445
• Primes having only {0, 8, 9} as digits.at n=13A385772
• Prime numbersat n=8726