cp's OEIS Frontend

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

%I A274187 #17 Dec 08 2016 11:31:54
%S A274187 4,12,24,24,120,5040,5040,362880,362880,3628800,39916800,6227020800,
%T A274187 6227020800,3379030566912000
%N A274187 Least number that is the product of n consecutive positive numbers and the product of 2 oblong numbers.
%e A274187 a(3) = 24 = 2*3*4 = 2*12.
%e A274187 a(6) = 5040 = 2*3*4*5*6*7 = 12*420 = 56*90.
%p A274187 N:= 10^10: # to get all terms <= N
%p A274187 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))}:
%p A274187 for n from 1 do
%p A274187   x:= n!;
%p A274187   for m from 1 while x <= N and not member(x, A072389) do
%p A274187     x:= x*(n+m)/m
%p A274187   od;
%p A274187   if x > N then break fi;
%p A274187   A[n]:= x;
%p A274187 od:
%p A274187 seq(A[i],i=1..n-1); # _Robert Israel_, Jun 16 2016
%Y A274187 Cf. A045619, A072389.
%K A274187 nonn,more
%O A274187 1,1
%A A274187 _Gionata Neri_, Jun 12 2016
%E A274187 a(14) from _Robert Israel_, Jun 16 2016