19813

Properties

Appears in sequences

• Primes which are not the sum of consecutive composite numbers.at n=41A037174
• Number of periodic palindromic structures of length n using a maximum of three different symbols.at n=20A056504
• Numbers k such that sigma(phi(sigma(k))) = phi(sigma(phi(k))).at n=16A067160
• Numbers k such that the digits of k^2 are exactly the same (albeit in different order) as the digits of (k+1)^2.at n=7A072841
• Sum of the primes in ordered 3 X 3 prime squares.at n=36A105089
• Numbers k such that k, k+1, k+2 and k+3 are 1,2,3,4-almost primes.at n=19A113000
• a(n)= A000265(3*(a(n-1)+a(n-2))/2 +1) starting at a(1)=1, a(2)=3.at n=25A124138
• 1 together with terms of A037174.at n=42A140464
• Primes congruent to 49 mod 61.at n=32A142847
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, 1, 1), (0, 1, 0), (1, -1, 1), (1, 1, -1)}.at n=9A148436
• Prime numbers p such that p^2 and (p+1)^2 are anagrams.at n=3A175519
• Number of 2 X 2 matrices with all elements in {0,1,...,n} and nonnegative determinant.at n=13A210290
• Number of (w,x,y,z) with all terms in {1,...,n} and w*x<=2*y*z.at n=13A211787
• Non-palindromic balanced primes in base 2.at n=37A256081
• Primes which are not the sum of two or more consecutive nonprime numbers.at n=39A257393
• E.g.f. satisfies A(x) = exp(x) * (1 + x * A(x)^2)^2.at n=4A377746
• Prime numbersat n=2242