21731

Appears in sequences

• Numbers that are the sum of 11 positive 8th powers.at n=41A003389
• Numbers that are the sum of 5 positive 9th powers.at n=10A003394
• Numbers that are the sum of at most 5 positive 9th powers.at n=35A004889
• Numbers k such that 171*2^k+1 is prime.at n=17A032462
• Number of partitions of n into parts but with two kinds of parts of sizes 1 to 7.at n=20A103926
• a(n) is the reverse concatenation of divisors of n.at n=20A176558
• a(n) = A176558(A175354(n)) = numbers m as reverse concatenations of divisors of numbers from A175354, where A175354 = numbers k such that reverse concatenations of divisors of k are nonprimes.at n=15A176588
• The Wiener index of the comb-shaped graph |_|_|...|_| with 2n (n>=1) nodes. The Wiener index of a connected graph is the sum of the distances between all unordered pairs of vertices in the graph.at n=30A192023
• Number of (n+5)X9 0..1 matrices with each 6X6 subblock idempotent.at n=10A224573
• Consider a number x. Take the sum of its digits. Repeat the process deleting the first addendum and adding the previous sum. The sequence lists the numbers that after some iterations reach the arithmetic derivative of x.at n=23A269312
• a(n) = (n-1)! + 1 mod n^3.at n=30A301317
• Numbers k of the form (x + y)*(x^2 + y^2) such that (x + y) and (x^2 + y^2) are primes.at n=34A349202