login
A367151
Primes whose reversals are triprimes.
2
29, 67, 89, 139, 223, 227, 233, 239, 269, 271, 277, 281, 421, 457, 461, 467, 499, 521, 523, 571, 577, 613, 617, 619, 653, 659, 809, 839, 881, 883, 887, 1049, 1123, 1289, 1373, 1459, 1543, 1579, 1609, 1783, 2003, 2011, 2017, 2027, 2029, 2053, 2081, 2087, 2141, 2143, 2213, 2221, 2237, 2239, 2243
OFFSET
1,1
LINKS
EXAMPLE
a(3) = 89 is a term because 89 is a prime and its reversal 98 = 2*7^2 is the product of 3 primes, counted with multiplicity.
MAPLE
rev:= proc(n) local L, i;
L:= convert(n, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L))
end proc:
select(t -> isprime(t) and numtheory:-bigomega(rev(t)) = 3, [seq(i, i=3..10000, 2)]);
MATHEMATICA
Select[Prime[Range[350]], PrimeOmega[FromDigits[Reverse[IntegerDigits[#]]]]==3&] (* Stefano Spezia, Nov 07 2023 *)
Select[Prime[Range[400]], PrimeOmega[IntegerReverse[#]]==3&] (* Harvey P. Dale, Jan 10 2024 *)
CROSSREFS
Sequence in context: A211492 A165238 A201022 * A118481 A245744 A141875
KEYWORD
nonn,base
AUTHOR
Robert Israel, Nov 06 2023
STATUS
approved