OFFSET
1,1
COMMENTS
A number is an emirpimes if it is a semiprime and if its reverse is a different semiprime. Thus palindromic semiprimes are excluded.
EXAMPLE
15 is the 5th triangular number. 15 = 3 * 5 and 51 = 3 * 17 are both semiprimes.
1891 is the 61st triangular number. 1891 = 31 * 61 and 1981 = 7 * 283 are both semiprimes.
3403 is the 82nd triangular number. 3403 = 41 * 83 and 3043 = 17 * 179 are both semiprimes.
MATHEMATICA
Select[Accumulate[Range[3200]], ! PalindromeQ[#] && PrimeOmega[#] == 2 && PrimeOmega[IntegerReverse[#]] == 2 &] (* Amiram Eldar, Aug 13 2024 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Massimo Kofler, Aug 13 2024
STATUS
approved