20404

Appears in sequences

• Number of subsets of { 1, ..., n } containing an A.P. of length 5.at n=16A018790
• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 84 ones.at n=19A031852
• A hierarchical sequence (S(W2{2}c) - see A059126).at n=10A059133
• Numbers n such that the number formed by the digits of 2n sorted in ascending order is equal to the sum of the divisors of n after the digits of each divisor have been sorted in ascending order.at n=6A083387
• Starting positions of strings of three 7's in the decimal expansion of Pi.at n=20A083631
• Number of words of length n over an alphabet of size 4 that are not "bifix-free".at n=8A094559
• A094559/4.at n=9A094578
• a(n) = A113572(n)/n.at n=5A113573
• Number of nondecreasing arrangements of n numbers x(i) in -(n+3)..(n+3) with the sum of sign(x(i))*2^|x(i)| zero.at n=8A187984
• Row sums of triangle A156070.at n=17A188538
• Numbers n such that there is no square n-gonal number greater than 1.at n=25A188896
• Number of arrays of 4 integers in -n..n with sum zero and adjacent elements differing in absolute value.at n=15A202964
• Let an integer with k+1 digits as n = d(k)*10^k + d(k-1)*10^(k-1) + ... + d(0)*10^0 and consider the transform T(n) = k*10^d(k) + (k-1)*10^d(k-1) + ... + 0*10^d(0). a(n) gives the fixed points of the transform T(n).at n=19A226767
• Number of (n+1) X (2+1) 0..6 arrays with every 2 X 2 subblock having its diagonal sum differing from its antidiagonal sum by 1, with no adjacent elements equal (constant-stress tilted 1 X 1 tilings).at n=2A234892
• Number of (n+1) X (3+1) 0..6 arrays with every 2 X 2 subblock having its diagonal sum differing from its antidiagonal sum by 1, with no adjacent elements equal (constant-stress tilted 1 X 1 tilings).at n=1A234893
• T(n,k) is the number of (n+1) X (k+1) 0..6 arrays with every 2 X 2 subblock having its diagonal sum differing from its antidiagonal sum by 1, with no adjacent elements equal (constant-stress tilted 1 X 1 tilings).at n=7A234898
• T(n,k) is the number of (n+1) X (k+1) 0..6 arrays with every 2 X 2 subblock having its diagonal sum differing from its antidiagonal sum by 1, with no adjacent elements equal (constant-stress tilted 1 X 1 tilings).at n=8A234898
• Sum of two consecutive primes that is also sum of two consecutive even positive squares.at n=7A236461
• Number of partitions p of n such that (maximal multiplicity of the parts of p) > (number of distinct parts of p).at n=41A240309
• Number of binary strings of length 2n having exactly 1 factorization as a concatenation of one or more even-length palindromes.at n=9A241208