23481

Appears in sequences

• Numbers k such that pi(k) = sopf(k) where sopf(k) is sum of distinct prime factors of k (A008472).at n=20A064444
• Numbers n whose sum of divisors and number of divisors are both triangular numbers.at n=42A070996
• Solution to the non-squashing boxes problem (version 1).at n=39A089054
• Numbers n such that 2*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.at n=11A102954
• a(n) = (p-1)! mod p^2 where p = n-th prime.at n=45A112660
• Number of n X n binary arrays symmetric under horizontal reflection with all ones connected only in a 110-111-110 pattern in any orientation.at n=11A146265
• Totally multiplicative sequence with a(p) = a(p-1) + 8 for prime p.at n=37A166705
• Number of (n+2) X (5+2) 0..3 arrays with every 3 X 3 subblock row and column sum not equal to 0 3 5 6 or 7 and every 3 X 3 diagonal and antidiagonal sum equal to 0 3 5 6 or 7.at n=21A252251
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 229", based on the 5-celled von Neumann neighborhood.at n=31A270948
• Terms k of A228058 such that gcd(k - A048250(k), A162296(k) - k) = A162296(k) - k.at n=34A325376
• Odd composites k such that sigma(k) has the same powerful part as k, where sigma is the sum of divisors function.at n=20A386425