A274187 Least number that is the product of n consecutive positive numbers and the product of 2 oblong numbers.

4, 12, 24, 24, 120, 5040, 5040, 362880, 362880, 3628800, 39916800, 6227020800, 6227020800, 3379030566912000

Offset: 1

Author

Gionata Neri, Jun 12 2016

Keywords

• nonn
• more

Examples

			a(3) = 24 = 2*3*4 = 2*12.
a(6) = 5040 = 2*3*4*5*6*7 = 12*420 = 56*90.
		

Crossrefs

Cf. A045619, A072389.

Programs

Maple

N:= 10^10: # to get all terms <= N
A072389:= {seq(seq(n*(n+1)*m*(m+1),m=n..floor((sqrt(1+4*N/(n*(n+1))-1)/2))),n=1..floor((sqrt(1+2*N)-1)/2))}:
for n from 1 do
  x:= n!;
  for m from 1 while x <= N and not member(x, A072389) do
    x:= x*(n+m)/m
  od;
  if x > N then break fi;
  A[n]:= x;
od:
seq(A[i],i=1..n-1); # Robert Israel, Jun 16 2016

Extensions

a(14) from Robert Israel, Jun 16 2016