OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..6000
EXAMPLE
14 is in the sequence because 13, 14 and 15 have only 1, 2 and 2 prime factors respectively, viz. 13, 2 * 7 and 3 * 5.
MAPLE
S:= select(t -> numtheory:-bigomega(t) <= 2, {$2..3000}):
sort(convert(S intersect map(`+`, S, 1) intersect map(`-`, S, 1), list)); # Robert Israel, Dec 15 2019
PROG
(PARI) isok(n) = (bigomega(n-1)>0) && (bigomega(n-1)<=2) && (bigomega(n)<=2) && (bigomega(n+1)<=2) \\ Michel Marcus, Jul 23 2013
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Walter Nissen, Aug 03 2005
STATUS
approved