20971520

Appears in sequences

• Expansion of (1+x)/(1-4*x).at n=12A003947
• a(n) = 5 * 2^n.at n=22A020714
• a(n) = n*2^n.at n=20A036289
• a(n) = n*omega(n)^n where omega(n) is the number of distinct prime divisors of n.at n=19A061340
• Expansion of g.f.: (1+x^2)/(1-2*x).at n=24A084215
• a(0)=1, a(1)=5, a(n+2)=4a(n), n>0.at n=23A084568
• a(n) = Sum_{k=0..n} binomial(n+(-1)^k, k).at n=23A087940
• Number of subsets of {1, ..., n} containing exactly one twin prime pair.at n=30A089882
• Number of subsets of {1,.., n} containing exactly one square.at n=26A089889
• Number of subsets of {1,.., n} containing exactly two squares.at n=25A089890
• Inverse binomial transform of n*Pell(n).at n=40A093968
• Expansion of (1 - 4*x + 6*x^2)/(1 - 2*x)^2.at n=21A097064
• a(n) = n*2^n - 2^(n/2)*sin(Pi*n/4).at n=20A099855
• Expansion of 4*x^4*(2 + x)/(1 - 2*x + 2*x^2 - 4*x^4 + 8*x^5 - 8*x^6).at n=45A100212
• Expansion of (1+x)^2/(1-4*x^2).at n=24A104721
• Smallest number beginning with 2 and having exactly n prime divisors counted with multiplicity.at n=22A106422
• Numbers of isomers of unbranched a-4-catapolyheptagons - see Brunvoll reference for precise definition.at n=13A121138
• Row sums of triangle A134400.at n=20A134401
• Binomial transform of A010685.at n=23A146523
• Number of binary strings of length n with equal numbers of 001 and 100 substrings.at n=25A164143