OFFSET
1,1
COMMENTS
In general, sequences of numbers divisible by primes p and q will have the form a(n+p+q-1) = a(n) + p*q.
The asymptotic density of this sequence is 5/13. - Amiram Eldar, Mar 25 2021
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,-1).
FORMULA
a(n+15) = a(n) + 39.
MAPLE
for n from 1 to 138 do if n mod 3 = 0 or n mod 13= 0 then print(n) fi od
MATHEMATICA
Select[Range[200], GCD[#, 39] > 1 &] (* T. D. Noe, Oct 15 2013 *)
With[{nn=60}, Join[3*Range[nn], 13*Floor[3/13 Range[nn]]]]//Union//Rest (* Harvey P. Dale, May 25 2020 *)
PROG
(PARI) is(n)=gcd(n, 39)>1 \\ Charles R Greathouse IV, Dec 11 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Gary Detlefs, Oct 11 2013
STATUS
approved