20886

Appears in sequences

• Numbers that are the sum of 4 positive 7th powers.at n=23A003371
• Aliquot sequence starting at 138.at n=15A008888
• Aliquot sequence starting at 150.at n=14A008889
• Aliquot sequence starting at 168.at n=12A008890
• Numbers whose base-12 representation has exactly 5 runs.at n=5A043654
• Number of rooted polycubes with n cells, with no symmetries removed.at n=5A048663
• Array read by antidiagonals: T(n,k) = number of rooted n-dimensional polycubes with k cells, with no symmetries removed (n >= 1, k >= 1).at n=33A048790
• Composite numbers k such that sigma(k) / d(k) is prime.at n=22A048969
• a(n) = Sum_{i=0..n} T(i,n-i), array T as in A049735.at n=21A049736
• usigma(n) = 2n + d(n), where d(n) is the number of divisors of n.at n=15A063829
• Aliquot sequence starting at 570.at n=10A074907
• Number of 4-step one space leftwards or up, two space rightwards or down asymmetric rook's tours on an n X n board summed over all starting positions.at n=20A187299
• G.f. A(x) satisfies A(x) = 1 + Sum_{n>=1} A(x)^n * x^n/(1 - x^(2*n)).at n=10A192401
• Number of primes of the form 1 + b^8 for 1 < b < 10^n.at n=5A215049
• Differences of the increasing arithmetic progression a^2+a, b^2+b, c^2+c, where b = 5*a+2, c = 7*a+3 and a >= 0.at n=29A260955
• Numbers n such that prime(n) contains a substring of all the prime digits in order, i.e., "2357".at n=7A295708
• Number of n X n 0..1 arrays with every element unequal to 0, 1, 2 or 3 king-move adjacent elements, with upper left element zero.at n=9A303720
• Numbers k such that s(k) = 2*k, where s(k) is the sum of divisors of k that have a square factor (A162296).at n=19A322609
• Consecutive states of the linear congruential pseudo-random number generator (1291*s + 4621) mod 21870 when started at s=1.at n=35A385337
• Numbers k such that sigma(k) = psi(k) + tau(k).at n=32A387953