19984

Appears in sequences

• Becomes prime or 4 after exactly 9 iterations of f(x) = sum of prime factors of x.at n=13A048131
• Numbers n such that phi(n) is a proper substring of n.at n=8A066663
• Numbers n such that the digits of n end in phi(n).at n=9A067206
• G.f.: q*Product_{k>0} (1-q^(12k))(1+q^(12k-1))(1+q^(12k-11))/(1-q^k).at n=33A098693
• Coefficients of a q-series inspired by Andrews and Ramanujan.at n=34A122928
• a(n) = 8*a(n-1) - 14*a(n-2) for n > 1; a(0) = 3, a(1) = 20.at n=5A164535
• Triangle of coefficients of polynomials u(n,x) jointly generated with A208930; see the Formula section.at n=53A208909
• Number of ways 1/n can be expressed as the sum of four distinct unit fractions: 1/n = 1/w + 1/x + 1/y + 1/z satisfying 0 < w < x < y < z.at n=24A241883
• Composite numbers n such that n - phi(n) is a power of 10.at n=6A248857
• The sum of the necessary diagonal movements from each square unit of an n X n+1 rectangle to reach any of the corners of the rectangle.at n=32A279034
• Number x = concat(MSD(x),b) such that MSD(x)*b = phi(x), where MSD(x) is the Most Significant Digit of x and phi(x) is the Euler totient function of x.at n=24A286130
• Sum of the prime parts in the partitions of n into 8 parts.at n=34A309469
• Starts of runs of 3 consecutive positive negaFibonacci-Niven numbers (A331085).at n=40A331087
• Positions of zeros in A345055, which is the Dirichlet inverse of A011772.at n=41A345053
• Numbers k such that A073734(k) is neither squarefree nor a prime power.at n=8A365899