OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
n=300: it is not a prime, 300 = 2*2*3*5*5; extremal prime factors are 2 and 5; gcd(2, 300/2) > 1 and gcd(5, 300/5) > 1, so neither 2 nor 5 is a unitary prime divisor of 300, thus 300 is in this sequence. - Labos Elemer, corrected by Jeppe Stig Nielsen, Jun 27 2017
MATHEMATICA
ma[x_] := Part[Reverse[Flatten[FactorInteger[x]]], 2] mi[x_] := Part[Flatten[FactorInteger[x]], 1] k=0; Do[s=mi[n]; s1=ma[n]; If[ !Equal[GCD[s, n/s], 1]&&!Equal[GCD[s1, n/s1], 1]&&!PrimeQ[n], Print[n]], {n, 2, 1000}]
PROG
(PARI) isA080366(n) = e=factor(n)[, 2]; e&&e[1]>1&&e[#e]>1 \\ Jeppe Stig Nielsen, Jun 27 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Feb 21 2003
STATUS
approved