21475

Appears in sequences

• Sum of 10 nonzero 8th powers.at n=37A003388
• Sums of terms of groups in A075621.at n=34A075625
• Numbers n such that n is not an odd prime and not a square of prime and the n-th Motzkin number == 1 (mod n).at n=3A081736
• Number of permutations of length n which avoid the patterns 1234, 2143, 3421.at n=26A116842
• Numbers k such that k^2 + 1 == 0 (mod 41^2).at n=25A157116
• a(n) = (1+n)*(9 + 11*n + 4*n^2)/3.at n=24A172482
• Numbers k such that (26*10^k - 131)/3 is prime.at n=25A272402
• Composite numbers m with sqrt(m) not prime such that T(m) == 1 (mod m), where the central trinomial coefficient T(m) is the coefficient of x^m in the expansion of (x^2+x+1)^m.at n=6A279821
• Partial sums of A299898.at n=34A299899
• Alternating sum of the numbers in the trajectory of n for the 3x+1 problem.at n=46A386437
• The maximal norm of an additively indecomposable element in Shanks' simplest cubic field Q[x]/(x^3 - n*x^2 - (n+3)*x - 1).at n=26A387575