140800

Appears in sequences

• Numbers k that divide the (left) concatenation of all numbers <= k written in base 21 (most significant digit on left).at n=16A029490
• Numbers k such that sigma(k)*phi(k)*k is a square.at n=14A114079
• Number of collinear triples of distinct points in Zn x Zn with no two on the same "horizontal" or "vertical" line.at n=15A146557
• a(n) = 20*a(n-1) - 96*a(n-2) for n > 1; a(0) = 1, a(1) = 10.at n=5A163165
• Numerators of fractions in the approximation of the square root of 5 satisfying: a(n)= (a(n-1)+ c)/(a(n-1)+1); with c=5 and a(1)=0. Also product of the powers of two and five times the Fibonacci numbers.at n=10A163305
• The number of labeled directed graphs (with self loops allowed) on n nodes of at most two colors, where no edge connects nodes of distinct colors.at n=4A197356
• Number of (w,x,y,z) with all terms in {1,...,n} and w + x > 2y + 2z.at n=32A212564
• The smallest k that is a Rhonda number in exactly n bases.at n=7A217986
• Expansion of Product_{k>=1} ((1+x^k)/(1-x^k))^(2*k-1).at n=13A261452
• Triangle read by rows: T(n,k) is the number of permutations pi of [n] such that pi has k+1 valleys and s(pi) avoids the patterns 132 and 321, where s is West's stack-sorting map (0 <= k <= floor((n-1)/2)).at n=37A319030
• Numbers k such that squarefree part of sigma(k) is equal to squarefree part of 2*k.at n=22A331752
• Number of copies of the star graph S(2,2,2) contained in the n-dimensional hypercube graph.at n=5A353029
• Numbers k such that A000005(k) = A000688(k).at n=25A369168
• Variation of triangle of Entringer numbers (A008281) read by rows: T(n, k) = T(n, k-1) + (n-2)*T(n-1, n-k) for 1 < k <= n, T(n, 1) = T(n-1, n-1) for n > 0, T(n, 0) = 0^n.at n=39A386363