18904
domain: N
Appears in sequences
- a(n) = (5*n+1)*(5*n+4).at n=27A001545
- a(n) = prime(n)*prime(n+1) - prime(n+1).at n=32A037167
- Numbers m such that 2*m - sigma(m) is a divisor of m and greater than one, where sigma = A000203 is the sum of divisors.at n=14A060326
- Number of non-associative non-commutative closed binary operations on a set of order n.at n=3A079192
- Even and odd solutions to abs(sigma(x)-2x) <= log(x). Numbers n whose abundance-radius does not exceed log(n).at n=40A088011
- Numbers k with abundance radius of 8, i.e., abs(sigma(k)-2*k) = 8.at n=10A088820
- Numbers n such that A001414(n) = sum of squared digits of n.at n=36A094908
- Numbers k such that k + sigma(k) + phi(k) is a fourth power.at n=1A116007
- Numbers k such that k + sigma(k) + phi(k) is a square.at n=27A116009
- Near-multiperfects with primes excluded, abs(sigma(m) mod m) <= log(m).at n=42A117347
- Near-multiperfects with primes and powers of 2 excluded, abs(sigma(m) mod m) <= log(m).at n=29A117348
- Near-multiperfects with primes, powers of 2 and 6 * prime excluded, abs(sigma(n) mod n) <= log(n).at n=29A117349
- Near-multiperfects with primes, powers of 2, 6 * prime and 2^n * prime excluded, abs(sigma(n) mod n) <= log(n).at n=13A117350
- Numbers k whose abundance sigma(k) - 2*k = -8. Numbers k whose deficiency is 8.at n=5A125247
- a(n) = n * (2*n + 1) * (6*n^2 + 4*n + 1) / 3.at n=8A132123
- Number of 6-step S, NW and NE-moving king's tours on an n X n board summed over all starting positions.at n=12A187380
- Integers k such that for all i > k the largest prime factor of i(i+1)(i+2)(i+3)(i+4)(i+5)(i+6) exceeds the largest prime factor of k(k+1)(k+2)(k+3)(k+4)(k+5)(k+6).at n=16A193948
- Number of nX2 0..3 arrays with no element equal to zero plus the sum of elements to its left or one plus the sum of elements above it or zero plus the sum of the elements diagonally to its northwest or one plus the sum of the elements antidiagonally to its northeast, modulo 4.at n=11A241392
- Deficient-perfect numbers: Deficient numbers n such that n/(2n-sigma(n)) is an integer.at n=29A271816
- Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 581", based on the 5-celled von Neumann neighborhood.at n=26A273071