20417

Appears in sequences

• Pseudoprimes to base 7.at n=29A005938
• Quadruples of different integers from [ 1,n ] with no common factors between triples.at n=30A015625
• Numerator of sum of -4th powers of divisors of n.at n=13A017671
• a(n) = (1/1 - 1/2 + ... + (-1)^(n-1)/n)*lcm{1..n}.at n=10A025530
• a(n) = T(n,n-3), where T is the array in A026374.at n=32A026382
• a(n) = T(n,n-3), where T is the array in A026386.at n=32A026394
• Number of partitions of n into parts not of the form 25k, 25k+6 or 25k-6. Also number of partitions with at most 5 parts of size 1 and differences between parts at distance 11 are greater than 1.at n=38A036005
• Numerators of coefficients in power series for -log(1+x)*log(1-x).at n=5A049281
• Number of base-2 Euler-Jacobi pseudoprimes (A047713) less than 10^n.at n=10A055551
• Numerator of the n-th alternating harmonic number, Sum_{k=1..n} (-1)^(k+1)/k.at n=10A058313
• Number of strongly unimodal partitions of n (strongly unimodal means strictly increasing then strictly decreasing).at n=35A059618
• Numbers k such that the smoothly undulating palindromic number (74*10^k - 47)/99 is a prime.at n=4A062223
• Base 4 expansion of 1/n has equal percentage of each digit 0,1,2,3.at n=23A074709
• Base 4 expansion of 1/n has equal percentage of each digit 0,1,2,3 (primitive values of n only).at n=20A074900
• Let u(1) = x and u(n+1) = (n^2/u(n)) + 1 for n >= 1; then a(n) is such that u(n) =(a(n)*x + b(n))/(c(n)*x + d(n)) (in lowest terms) and a(n), b(n), c(n), d(n) are positive integers.at n=10A075827
• Let u(1) = x and u(n+1) = (n^2/u(n)) + 1 for n >= 1; then a(n) is such that u(n) = (b(n)*x + c(n))/(a(n)*x + d(n)) (in lowest terms) and a(n), b(n), c(n), d(n) are positive integers.at n=11A075830
• Numbers k where the root mean square (RMS) of k and 7 is an integer, i.e., sqrt((k^2 + 7^2)/2) is an integer.at n=14A076293
• Numerator of the product of n and the n-th alternating harmonic number, Sum_{k=1..n} (-1)^(k+1)/k.at n=10A119787
• Absolute value of numerator of the sum of all elements of the n X n matrix M with M[i,j] = (-1)^(i+j)*i/j for i,j = 1..n.at n=10A120301
• a(n) = Sum{i=1..n} ( i*2^(i-1) ) - ( A002024(n)*(A002024(n)+1)/2 - n ) * 2^(A002024(n)-1).at n=10A135471