23869

Properties

Appears in sequences

• Least odd prime divisor of prime(n)*prime(n-1) - 1, or 1 if prime(n)*prime(n-1) - 1 is a power of 2.at n=63A023519
• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 90 ones.at n=22A031858
• Least prime in A023200 (lesser of 4-twins) such that the distance to the next 4-twin is 6*n.at n=17A052351
• Number of compositions of the integer n into positive parts that avoid a fixed pattern of three letters.at n=17A102726
• Primes in A128490.at n=24A128491
• Prime numbers p such that p +- ((p-1)/6) are primes.at n=25A137724
• Primes of the form 4*n^2 + 2*n -1.at n=37A155737
• Number of lines through at least 2 points of a 9 X n grid of points.at n=36A160849
• Primes of the form ((p+1)/2)^2+((p-1)/2), where p is prime.at n=27A163419
• Primes of the form p + (p^2 - 1)/8, where p is also prime.at n=21A165352
• Primes of the form (p^2-1)/4-p where p are also primes.at n=24A165557
• Primes of the form A177353(n) + 1 sorted with respect to increasing n.at n=45A178178
• Primes of form a^2+b^2 such that a^4+b^4 and a^8+b^8 are primes.at n=20A182313
• Primes p congruent to 1 mod 12 such that (p + 1)/2 does not divide the numerator of the Bernoulli number B(p + 1).at n=26A232039
• Centered 18-gonal (or octadecagonal) primes.at n=20A264825
• Primes for which the concatenation of the digits in the even positions and the concatenation of the digits in the odd positions are squares.at n=33A275797
• Number of 2 X n 0..1 arrays with every element both equal and not equal to some elements at offset (-1,-1) (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero.at n=10A278281
• Primes that can be generated by the concatenation in base 6, in descending order, of two consecutive integers read in base 10.at n=15A287307
• Primes p such that q^2 - p^2 + 1 is the square of a composite number where p and q are consecutive primes.at n=26A316934
• Primes p such that d(p^2-1) sets a record, where d(n) is the number of divisors of n.at n=25A335325