18811

Appears in sequences

• a(n) = smallest number > a(n-1) such that a(1)*a(2)*...*a(n) + 1 and a(1)*a(2)*...*a(n) - 1 are primes.at n=40A051956
• Squares of 1 and primes, written backwards.at n=29A060998
• Semiprimes whose digit reversal is a nontrivial power.at n=39A108849
• Semiprimes (A001358) whose digit reversal is a square.at n=34A115710
• Numbers consisting of ones and eights.at n=42A213084
• Number of (w,x,y) with all terms in {0,...,n} and w != min(|w-x|, |x-y|).at n=26A213499
• Sp = reversal of some square s where s = x^2 for x = 1,2,.. (ignoring leading zeros). Sp is in the sequence if it is semiprime.at n=29A242097
• Triangle of number of interval-closed sets T(m,n) in the product of two chains [m]x[n], for m <= n, read by rows.at n=47A367109
• a(n) is the smallest positive integer k with k != 10^m (m: nonnegative integer) for which 1/n can be obtained by incorrectly reducing k/(n*k) - by deleting the same digit in the numerator and denominator as often as possible, leaving one digit "1" in the numerator.at n=46A370911