21117

Appears in sequences

• Prefix primes in base 8 (written in base 8).at n=45A024768
• Positions of 4-digit terms in the continued fraction for Pi (3 is at position 0).at n=18A048959
• Discriminants of real quadratic fields with class number 1 and related continued fraction period length of 22.at n=49A051963
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (-1, 0, 0), (-1, 0, 1), (1, -1, -1), (1, 1, 0)}.at n=9A149108
• Number of (w,x,y,z) with all terms in {1,...,n} and min{|w-x|,|w-y|}=min{|x-y|,|x-z|}.at n=23A212579
• Principal diagonal of the convolution array A213555.at n=8A213556
• Row 5 of A277710: Positions of 5's in A264977; positions of 10's in A277330.at n=41A277715
• Numbers of the form HMMSS with primes H < 24 and MM, SS < 60, for which the number of seconds after midnight, 3600*H+60*MM+SS, is also prime.at n=22A295011
• G.f. A(x) satisfies: A(x) = (1/(1 - x)) * A(x^2)^2*A(x^3)^3*A(x^4)^4* ... *A(x^k)^k* ...at n=15A307604
• G.f.: Product_{j>=1} (1 + p(x^j)), where p(x) is the g.f. of A000040.at n=18A309950
• Number of 4 dots bracelet partitions of n.at n=12A328542
• a(n) is the least number k such that {k, k^2, ..., k^n} are all odious numbers (A000069), but k^(n+1) is not.at n=11A345399