20366

Appears in sequences

• a(n) = (d(n)-r(n))/2, where d = A026043 and r is the periodic sequence with fundamental period (1,1,0,0).at n=46A026044
• Number of tree-like heptagonal systems.at n=8A036757
• a(n) = n*(n^4 + 10*n^3 + 35*n^2 + 50*n + 144)/120.at n=16A051745
• Squarefree n such that the elliptic curve n*y^2 = x^3 - x arising in the "congruent number" problem has rank 3.at n=34A062693
• Numbers k such that 216*k+108 is a term of A097703 and A007494 and A098240.at n=19A098241
• Numbers k such that absolute value of 7^k - k^7 is prime.at n=5A128447
• Numbers n such that sigma(n) and sigma(sigma(n)) are both perfect squares.at n=22A134263
• Expansion of 1/(1 - x^3 - x^4 - x^5 + x^8)^2.at n=35A147851
• Largest k such that k! < 2^(2^n).at n=18A152909
• The number of permutations of length n that can be sorted by 3 pop stacks in parallel.at n=8A164871
• Number of permutations p of [n] with no fixed points and displacement of elements restricted by five: 1 <= |p(i)-i| <= 5.at n=9A259778
• Number of compositions of n such that the maximal distance between two identical parts equals three.at n=18A262196
• Numbers k such that (73*10^k + 143)/9 is prime.at n=23A272193
• a(n) = n * Sum_{d|n} binomial(d+4,5)/d.at n=16A343546