19728

Appears in sequences

• Numbers k such that k and 4*k are anagrams.at n=10A023088
• Theta series of 8-dimensional strongly 6-modular lattice O(6) with minimal norm 3.at n=33A029720
• Number of partitions in parts not of the form 15k, 15k+1 or 15k-1. Also number of partitions with no part of size 1 and differences between parts at distance 6 are greater than 1.at n=48A035955
• a(1)=1. a(n+1) = sum a(k), where the sum is over all positive integers k, k <= n, where each positive integer <= k and coprime to k is also coprime to n.at n=21A124693
• a(n) = floor(log_10(2^(2^n))).at n=15A129784
• Number of (w,x,y,z) with all terms in {1,...,n} and w^2>x^2+y^2+z^2.at n=20A212094
• Product between n-th prime and next perfect square.at n=32A229497
• Number of weak peaks in all Motzkin paths of length n. A weak peak of a Motzkin path is a vertex on the top of a hump. A hump is an upstep followed by 0 or more flatsteps followed by a downstep. For example, the Motzkin path u*duu*h*h*dd, where u=(1,1), h=(1,0), d(1,-1), has 4 weak peaks (shown by the stars).at n=11A247287
• Number of permutations of length n in the class of juxtapositions of separable permutations with 21-avoiders.at n=8A326348
• Numbers k such that each of k, k+1, k+2, and k+4 is a sum of two squares.at n=26A328224
• Numbers k such that k*p is divisible by k+p, where p > 0 and p = A007954(k) = the product of digits of k.at n=13A334679
• a(n) = coefficient of x^n in A(x) such that 2 = Sum_{n=-oo..+oo} (-x)^n * (2*A(x) + x^(n-1))^(n+1).at n=6A359712
• a(n) = Sum_{k=0..floor(n/3)} 2^(n-3*k) * binomial(k,n-3*k)^2.at n=25A387516