19801

Properties

Appears in sequences

• Smallest primitive prime factor of Fibonacci number F(n), or 1 if F(n) has no primitive prime factor.at n=32A001578
• Primes that are palindromic in base 2 (but written here in base 10).at n=35A016041
• Convolution of odd numbers and A001950.at n=27A023659
• Primes of the form j^2 + (j+1)^2.at n=34A027862
• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 94 ones.at n=18A031862
• a(n) = F(n) / Product_{p|n} F(p), where F(k) is k-th Fibonacci number and the p's in product are the distinct primes dividing n.at n=32A051348
• Largest prime factor of n-th Fibonacci number.at n=30A060385
• Primitive part of Fibonacci(n).at n=32A061446
• Factorize the Fibonacci numbers in order, skipping F(0)-F(2), F(6)=8 and F(12)=144; at each step at least one new prime will occur; append to the sequence the smallest such new prime.at n=28A061488
• Prime hypotenuses of Pythagorean triangles with a prime leg.at n=13A067756
• Centered 20-gonal (or icosagonal) numbers.at n=44A069133
• a(n+1) - 3*a(n) + a(n-1) = (2/3)(1+w^(n+1)+w^(2n+2)), where w = exp(2 Pi I / 3).at n=11A071618
• Numbers n such that the absolute value of the real part of (1+2*I)^n is prime.at n=21A073019
• Numbers k such that 1/(1/phi(k) + 1/phi(k+1) + 1/phi(k+2) + 1/phi(k+3)) is an integer.at n=16A073544
• a(n) = A077741(n)/n.at n=36A077742
• Downward vertical of triangular spiral in A051682.at n=33A081272
• Balanced primes of order four.at n=18A082079
• Difference between the arithmetic mean of the neighbors of the terms and the term itself follows the pattern 0,1,2,3,4,5,...at n=40A086514
• Smallest prime of the form 1 followed by a perfect power.at n=21A089773
• Expansion of x*(1+3*x+2*x^2)/((1+x+x^2)*(1-x-x^2)).at n=21A100886