15519504

Appears in sequences

• a(n) = 4*(2n+1)!/n!^2.at n=10A002011
• a(n) = denominator of harmonic number H(n) = Sum_{i=1..n} 1/i.at n=19A002805
• a(n) = (n+1)*binomial(n+1,11).at n=11A027771
• a(1) = 1. a(n) = n*a(n-1) if gcd(n,a(n-1)) = 1, a(n-1)/n if n divides a(n-1), otherwise a(n) = a(n-1).at n=18A068629
• a(1) = 1. a(n) = n*a(n-1) if gcd(n,a(n-1)) = 1, a(n-1)/n if n divides a(n-1), otherwise a(n) = a(n-1).at n=19A068629
• a(n) = denominator of the sum of reciprocals of the terms in n-th row of triangle A077581.at n=22A126578
• a(n) = denominator of sum{k=1 to n} 1/A127518(k).at n=19A127520
• a(n) = denominator of sum{k=1 to n} 1/A127518(k).at n=20A127520
• Denominator of the polynomial A_l(x) = Sum_{d=1..l-1} x^(l-d)/d for index l=2n+1 evaluated at x=1.at n=9A145610
• Sum of squared terms in rows of triangle A152547: a(n) = Sum_{k=0..C(n,[n/2])-1} A152547(n,k)^2.at n=21A152548
• Denominator of the Harary number for the cycle graph C_n.at n=40A160047
• Denominator of sum of reciprocals of numbers less than n that do not divide n.at n=20A281086
• a(0) = 1; for n >= 1, a(n) = A059897(n, a(n-1)).at n=21A284567
• a(n) = 20160*(3*n)!/(n!*(n+3)!^2).at n=7A361030
• a(n) = n*binomial(n, n/2) if n is even otherwise 2^(n-1)*binomial(n-1, (n-1)/2).at n=22A389423