A367151 Primes whose reversals are triprimes.

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

Robert Israel, Table of n, a(n) for n = 1..10000

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

Cf. A014612, A085778.

Sequence in context: A211492 A165238 A201022 * A118481 A245744 A141875

Adjacent sequences: A367148 A367149 A367150 * A367152 A367153 A367154

Keyword

nonn,base

Author

Robert Israel, Nov 06 2023

Status

approved