1572863

Appears in sequences

• a(0) = 1; a(n) = 3*2^n - 1, for n > 0.at n=19A052940
• a(2n) = 2*2^n - 1, a(2n+1) = 3*2^n - 1.at n=39A052955
• a(0) = 0; for n > 0, a(n) = 3*2^(n-1) - 1.at n=20A055010
• Smallest number x > 1 such that phi(x) + sigma(x) = k*d(x)^n, i.e., the left-hand side is divisible by the n-th power of the number of divisors.at n=9A055470
• a(n) = n*8^n - 1.at n=5A064754
• Variation on Ulam numbers: a(1) = 1; a(2) = 2; for n>2, a(n) = smallest (n odd) or largest (n even) number > a(n-1) that is a unique sum of two distinct earlier terms.at n=39A081026
• a(0) = 1; for n > 0, a(n) = 3*2^(n-1) - 1.at n=20A083329
• Add 1, double, add 1, double, etc.at n=39A083416
• a(n) = 3*2^floor((n-1)/2) + (-1)^n.at n=38A097581
• Expansion of g.f.: (3+x+2*x^2-2*x^3)/((1-2*x)*(1+x^2)).at n=19A100720
• Smallest semiprime with Hamming weight n (i.e., smallest semiprime with exactly n ones when written in binary), or -1 if no such number exists.at n=19A102029
• Slater-Velez permutation sequence of the 2nd kind.at n=38A129198
• a(n) = 6*4^n - 1.at n=9A140529
• a(n) = 3*(-1)^(n+1)*2^n - 1.at n=19A140683
• a(n) = 3*2^n - 1.at n=19A153893
• Numbers of the form i*8^j-1 (i=1..7, j >= 0).at n=47A165804
• a(n) = 6*8^n-1.at n=6A198854
• Numbers k such that A249441(k) = 3.at n=32A249452
• Numbers n such that the Shevelev polynomial {m, n} has a root at m = -1.at n=28A264613
• Independence number of the n-Mycielski graph.at n=21A266550