210210

Appears in sequences

• a(n) = 3*(n+1)*binomial(n+2,6).at n=9A027779
• a(n) = 5*(n+1)*binomial(n+2,10).at n=5A027783
• Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 2,1,0.at n=5A037527
• a(1)=1, a(2)=2; thereafter, a(n) is the smallest number m not yet in the sequence such that every prime that divides a(n-1) also divides m.at n=41A060735
• If n | a(n) then a(n+1) = a(n)/(highest power of n that divides a(n)), otherwise a(n+1) = n*a(n); a(0) = 1.at n=15A065422
• Numbers k such that phi(k) < k/5.at n=26A066765
• a(n) = Sum_{k=1..(p-1)*(p-2)} floor((k*p)^(1/3)) where p is the n-th prime.at n=18A078838
• Integers n for which the ratio phi(n)/pi(n) is smaller than for any subsequent n. Here phi(n) is Euler's totient function and pi(n) is the number of primes that are at most n.at n=27A080289
• T(n,k) = binomial(n,2*k)*binomial(2*k,k) for 0 <= k <= n, triangle read by rows.at n=109A089627
• Triangle read by rows: T(n,k)=(1/2)*C(n+k,k)*C(n,n-k).at n=41A092370
• a(n) = binomial(n+4,4) * binomial(n+8,4).at n=6A104475
• a(n) = binomial(n+6,n)*binomial(n+10,n).at n=4A105253
• a(n) = product[k=1..n] P(k), where P(k) is the largest prime <= 2*k. a(n) = product[k=1..n] A060308(k).at n=6A118747
• Numbers k such that 2*k-1, 4*k-1, 6*k-1, 8*k-1 and 10*k-1 are primes.at n=14A124488
• Ternary numbers with equal numbers of 0's, 1's and 2's and such that read left-to-right at all times the number of 2's >= number of 1's >= number of 0's.at n=1A134236
• Numbers with exactly 6 distinct prime divisors {2,3,5,7,11,13}.at n=6A147573
• Largest solution to phi(x) = n!, where phi() is Euler totient function (A000010).at n=7A165774
• Number of permutations of 0..floor((n*4-1)/2) on even squares of an n X 4 array such that each row and column of even squares is increasing.at n=6A215288
• Number of permutations of 0..floor((n*7-1)/2) on even squares of an nX7 array such that each row and column of even squares is increasing.at n=3A215291
• T(n,k)=Number of permutations of 0..floor((n*k-1)/2) on even squares of an nXk array such that each row and column of even squares is increasing.at n=48A215292