21081

Appears in sequences

• Number of fusenes with 26 hexagons, C_(2v) symmetry and containing n carbon atoms.at n=10A123662
• Numbers whose square starts with 4 identical digits.at n=20A132391
• Numbers k such that k^6 - 2 and k^6 + 2 are both primes.at n=30A154938
• a(n) = 13*n^2 + 7*n + 1.at n=39A168240
• Odd numbers k such that phi(k) and cototient(k) have the same prime signature.at n=27A280927
• Numbers k such that (2*10^k - 23)/3 is prime.at n=17A293000
• Number of compositions (ordered partitions) of n into square parts (A000290) such that no two adjacent parts are equal (Carlitz compositions).at n=61A301503
• Sum of the largest parts of the partitions of n into 9 parts.at n=36A326473
• Numbers k such that k, k+1, k+2, k+3 and k+4 are terms of A288041.at n=2A336221
• For 1<=x<=n, 1<=y<=n, with gcd(x,y)=1, write 1 = gcd(x,y) = u*x+v*y with u,v minimal; a(n) = sum of the values of u^2+v^2.at n=27A345431
• Numbers whose square starts with exactly 4 identical digits.at n=19A346940