399168

Appears in sequences

• a(n) = n! with trailing zeros omitted.at n=11A004154
• a(n) = n^2*(n+1)!/(n^tau(n)) where tau(n) is the number of divisors of n.at n=9A069141
• A unitary phi reciprocal amicable number: consider two different numbers r, s which satisfy the following equation for some integer k: uphi(r) = uphi(s) = (1/k) * r * s / (r-s); or equivalently, 1/uphi(r) = 1/uphi(s) = k * (1/s - 1/r); sequence gives r numbers.at n=25A080766
• a(1)=1, a(n) = Sum_{k=1..n-1} Fibonacci(k)*a(k).at n=8A082471
• The sum of the two numbers in an amicable pair, A002025(n) + A002046(n).at n=21A180164
• a(n) = 24*n*p(n) = 24*n*A000041(n).at n=20A183009
• Number of nX4 0..1 arrays avoiding 0 0 1 and 0 1 0 horizontally and 0 0 1 and 0 1 1 vertically.at n=12A207119
• The sum (in nondecreasing order) of the two numbers in an amicable pair.at n=21A259953
• Zeroless factorials (version 2): a(0) = 1, and for any n > 0, a(n) = noz(1 * noz(2 * ... * noz((n-1) * n))), where noz(n) = A004719(n) omits the zeros from n.at n=11A321475
• Denominators of the fractions f(n) such that (6/Pi^2)*f(n) is the asymptotic density of the numbers k with A280292(k) = sopfr(k) - sopf(k) = n.at n=11A338560
• Lexicographically least strictly increasing sequence such that, for any n > 0, Sum_{k = 1..n} 1/a(k) can be computed without carries in factorial base.at n=6A343522
• Integers k such that k/A097621(k) is an integer.at n=33A344826
• Omit zero digits from factorial numbers.at n=11A356757
• Irregular triangle (an infinite binary tree) read by rows. The tree has root node 1 in row n = 1. For n > 1, each node with value m in row n-1 has a left child with value m / n if n divides m, and a right child with value m * n.at n=35A360298
• a(n) is the least number with exactly n divisors of the form 5*k+1.at n=33A364586
• a(n) is the least number with exactly n divisors of the form 5*k+2.at n=36A364598
• a(n) is the least number with exactly n divisors of the form 5*k+4.at n=36A364600
• a(n) is the denominator of the probability that a particular one of the A335573(n+1) fixed polyominoes corresponding to the free polyomino with binary code A246521(n+1) appears in the version of the Eden growth model described in A367671 when n square cells have been added.at n=21A367676
• Numbers k such that both A381019(k) and A381019(k+1) are composite.at n=15A381120