OFFSET
1,1
COMMENTS
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
1640 is oblong (1640 = 40*41) and 1639 = 11*149, 1641 = 3*547 are both semiprime.
MAPLE
select(t -> numtheory:-bigomega(t+1)=2 and numtheory:-bigomega(t-1)=2, [seq(i*(i+1), i=1..1000)]); # Robert Israel, Nov 28 2016
PROG
(PARI) for(i=1, 250, n=i*(i+1); if(bigomega(n-1)==2&&bigomega(n+1)==2, print1(n, ", ")))
CROSSREFS
KEYWORD
nonn
AUTHOR
Antonio Roldán, Nov 16 2016
STATUS
approved