OFFSET
1,2
COMMENTS
Multiplied by 2 we have 4,10,16,18,... which is the set of even terms of A153329. - R. J. Mathar, Jan 23 2009
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = (A053178(n)-1)/10. - R. J. Mathar, Oct 30 2009
EXAMPLE
Distribution of the terms in the following triangular array:
*;
*,*;
2,*,*;
*,*,*,8;
*,*,*,*,12;
*,*,9,*,*,*;
*,*,*,*,*,*,*;
5,*,*,*,*,22,*,*;
*,*,*,17,*,*,*,*,36;
*,*,*,*,23,*,*,*,*,44;
*,*,16,*,*,*,*,39,*,*,*; etc.
where * marks the non-integer values of (2*h*k + k + h)/5 with h >= k >= 1. - Vincenzo Librandi, Jan 15 2013
MAPLE
q:= n-> not isprime(10*n+1):
select(q, [$0..120])[]; # Alois P. Heinz, Jan 21 2021
MATHEMATICA
Select[Range[0, 200], !PrimeQ[10*# + 1]&] (* Vincenzo Librandi, Jan 12 2013 *)
PROG
(Magma) [n: n in [0..150] | not IsPrime(10*n + 1)]; // Vincenzo Librandi, Jan 12 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Dec 22 2008
EXTENSIONS
63 replaced by 53 by R. J. Mathar, Jan 23 2009
0 added by Arkadiusz Wesolowski, Aug 03 2011
STATUS
approved