21517

Properties

Appears in sequences

• Primes that remain prime through 3 iterations of function f(x) = 2x + 3.at n=31A023273
• Number of distinct n-digit suffixes of base 6 squares not containing digit 0.at n=8A038120
• Denominators of continued fraction convergents to sqrt(931).at n=11A042801
• Generalized Catalan numbers C(6; n).at n=5A064089
• Sixth diagonal of triangle A064094.at n=6A064302
• Primes which are the concatenation of numbers n_1, n_2, n_3, in that order, with n_1 + n_2 = n_3 (leading zeros are forbidden for nonzero n_i).at n=35A067860
• Initial term in sequence of four consecutive primes separated by 3 consecutive differences each <=6 (i.e., when d=2,4 or 6) and forming d-pattern=[4,2,6]; short d-string notation of pattern = [426].at n=12A078850
• Consider the mapping f(a/b) = (a^2 + b)/(a^2 - b). Taking a =2, b = 1 to start with and carrying out this mapping repeatedly on each new (reduced) rational number gives the following sequence 2/1,5/3,14/11,207/185,... Sequence contains the numerator.at n=4A081483
• Primes in which the digit string can be partitioned into three parts such that the sum of the first two is equal to the third, and the second part is nonzero.at n=34A088291
• Group the natural numbers so that the n-th group contains n numbers whose sum as well as the group product +1 is prime. Sequence contains the primes arising as the sum of the terms of groups.at n=34A092946
• Smallest prime in kx^3+x+5 is prime.at n=40A114369
• Primes congruent to 41 mod 59.at n=37A142768
• Primes congruent to 45 mod 61.at n=38A142843
• Primes of the form 20*k^2 + 32*k + 13.at n=16A154414
• Number of n X n 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 1 0 and 1 0 1 vertically.at n=4A207461
• Number of nX5 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 1 0 and 1 0 1 vertically.at n=4A207464
• T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 1 0 and 1 0 1 vertically.at n=40A207467
• Number of 5Xn 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 1 0 and 1 0 1 vertically.at n=4A207469
• Primes p such that p+12, p+1234 and p+123456 are also prime.at n=9A236304
• Number of partitions p of n containing floor((min(p) + max(p))/2) as a part.at n=42A238482