20129

Properties

Appears in sequences

• Primes that remain prime through 3 iterations of function f(x) = 5x + 4.at n=27A023284
• Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 12.at n=14A031600
• Base 4 expansion of 1/n has equal percentage of each digit 0,1,2,3.at n=22A074709
• Base 4 expansion of 1/n has equal percentage of each digit 0,1,2,3 (primitive values of n only).at n=19A074900
• A014486-indices of A083932-trees.at n=38A083934
• Row sums of triangle A089940.at n=13A089941
• Number of walks of length n between two nodes at distance 3 in the cycle graph C_7.at n=14A095308
• Indices where A138554 requires only squares < floor(sqrt(n))^2.at n=41A138555
• Primes p1 such that p1^3+p2^2=pp are average of twin primes. p1 and p2 consecutive primes, p1 < p2.at n=15A138735
• Primes congruent to 10 mod 59.at n=38A142737
• Primes congruent to 60 mod 61.at n=33A142858
• Primes p of the form 4*k+1 for which s=26 is the least positive integer such that s*p-(floor(sqrt(s*p)))^2 is a square.at n=24A145050
• Primes p such that p^2 - 2 is a 5-almost prime.at n=33A156620
• Sequence of primes separated by [sequence of prime] elements. 2, [find 2nd prime after 2 = ] 5, [find 3rd prime after 5 =] 13, [find 5th prime after 13 =] 61, ..., etc.at n=35A180302
• Number of nX3 binary arrays without the pattern 0 0 1 vertically or horizontally.at n=5A188757
• Number of nX6 binary arrays without the pattern 0 0 1 vertically or horizontally.at n=2A188760
• T(n,k)=Number of nXk binary arrays without the pattern 0 0 1 vertically or horizontally.at n=30A188763
• T(n,k)=Number of nXk binary arrays without the pattern 0 0 1 vertically or horizontally.at n=33A188763
• Triangle read by rows: T(n,k) (n>=1, 1 <= k <= n) = number of n-element unlabeled rigid interval posets of height k.at n=49A193357
• T(n,k)=Number of nXk 0..1 arrays avoiding 0 1 0 horizontally and 1 0 0 vertically.at n=33A206889