21730

Appears in sequences

• a(n) = 4*a(n-1) - a(n-2) - 4, with a(0) = 2, a(1) = 4.at n=8A071954
• a(0)=a(1)=1; a(n) = lcm(a(n-1) + a(n-2), n).at n=10A128977
• a(n) = n*A002088(n).at n=40A143270
• Place a(n) red and b(n) blue balls in an urn; draw 6 balls without replacement; Probability(6 red balls)=Probability(4 red and 2 blue balls); binomial(a(n),6)=binomial(a(n),4)*binomial(b(n),2).at n=9A179123
• The number of triangles in an equipotential triangle divided by medians into n rows of smaller triangles.at n=13A210687
• Triangle of coefficients of polynomials v(n,x) jointly generated with A210858; see the Formula section.at n=48A210859
• Numbers k that are the product of four distinct primes such that x^2+y^2 = k has integer solutions.at n=36A248712
• Number of (n+2)X(5+2) 0..1 arrays with every 3X3 subblock sum of the two sums of the diagonal and antidiagonal minus the two minimums of the central column and central row nondecreasing horizontally, vertically and ne-to-sw antidiagonally.at n=5A254904
• Number of (6+2)X(n+2) 0..1 arrays with every 3X3 subblock sum of the two sums of the diagonal and antidiagonal minus the two minimums of the central column and central row nondecreasing horizontally, vertically and ne-to-sw antidiagonally.at n=4A254912
• a(n) = 2*a(n-1) - a(n-3) + a(floor(n/2)) + a(floor(n/3)) + ... + a(floor(n/n)), where a(0) = 1, a(1) = 2, a(2) = 3.at n=15A298407
• Number of n X n 0..1 arrays with every element equal to 0, 2, 3, 4, 6 or 7 king-move adjacent elements, with upper left element zero.at n=4A299215
• Number of n X 5 0..1 arrays with every element equal to 0, 2, 3, 4, 6 or 7 king-move adjacent elements, with upper left element zero.at n=4A299218
• T(n,k) = Number of n X k 0..1 arrays with every element equal to 0, 2, 3, 4, 6 or 7 king-move adjacent elements, with upper left element zero.at n=40A299221
• Sum of sums of omegas of the parts over all strict integer partitions of n.at n=47A325515
• a(n) = (p-1)! mod p^3, where p = prime(n).at n=10A330526