|
|
A336263
|
|
Numbers of the form k + s + 2*k*s where k is a positive integer and s is a Sundaram number (A159919).
|
|
1
|
|
|
13, 22, 31, 37, 40, 49, 52, 58, 62, 67, 73, 76, 82, 85, 87, 94, 97, 103, 112, 115, 121, 122, 127, 130, 136, 137, 139, 142, 148, 157, 162, 166, 171, 172, 175, 178, 181, 184, 187, 192, 193, 199, 202, 211, 212, 214, 217, 220, 227, 229, 232, 237, 238, 241, 247, 253, 256
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
If a term s in A159919 is not here, 2*s+1 is a semiprime.
|
|
LINKS
|
|
|
EXAMPLE
|
4 is a Sundaram number, therefore 1+4+2*4*1=13 is a term, and (13*2)+1=27 is not a semiprime.
|
|
MATHEMATICA
|
Select[Range[2^8], PrimeOmega[2*# + 1] >= 3 &] (* Amiram Eldar, Jul 15 2020 *)
|
|
PROG
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|