OFFSET
1,1
COMMENTS
n^2+n+41 is sometimes referred to as Euler's polynomial.
Subsequence of A228184.
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..10000
EXAMPLE
65 = 5 * 13 is semiprime and 65^2 + 65 + 41 = 4331 = 61 * 71 is also semiprime so 65 is in the sequence.
87 = 3 * 29 is semiprime and 87^2 + 87 + 41 = 7697 = 43 * 179 is also semiprime so 87 is in the sequence.
6 = 2 * 3 is semiprime but 6^2+6+41 = 83 is prime (not semiprime) so 6 is not in the sequence.
MAPLE
MATHEMATICA
c = 0; Do[If [PrimeOmega[n] == 2 && PrimeOmega[n^2 + n + 41] == 2, c++; Print[c, " ", n]], {n, 1, 10^5}];
Select[Range[500], PrimeOmega[#]==PrimeOmega[#^2+#+41]==2&] (* Harvey P. Dale, Nov 07 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
K. D. Bajpai, May 20 2014
STATUS
approved