A046368 Products of two palindromic primes.

4, 6, 9, 10, 14, 15, 21, 22, 25, 33, 35, 49, 55, 77, 121, 202, 262, 302, 303, 362, 382, 393, 453, 505, 543, 573, 626, 655, 706, 707, 746, 755, 766, 905, 917, 939, 955, 1057, 1059, 1111, 1119, 1149, 1267, 1337, 1441, 1454, 1514, 1565, 1574, 1594, 1661, 1765, 1838, 1858

Offset: 1

Author

Patrick De Geest, Jun 15 1998

Keywords

• nonn
• base

Comments

Intersection of A001358 and A033620; A046368 is a subsequence. - Reinhard Zumkeller, Apr 10 2011

Equivalently, semiprimes where both prime factors are palindromes. - Franklin T. Adams-Watters, Apr 11 2011

See A046376 for the subsequence of palindromic terms. - M. F. Hasler, Jan 04 2022

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A001358 (semiprimes), A002113 (palindromes), A002385 (palindromic primes), A046376 (subsequence of palindromes), A046400.

Programs

Mathematica

palQ[n_] := Reverse[x = IntegerDigits[n]] == x; Select[Range[1800], PrimeOmega[#] == 2 && And @@ palQ /@ First /@ FactorInteger[#] &] (* Jayanta Basu, Jun 23 2013 *)

PARI

select( {is_A046368(n)=bigomega(n)==2 && vecmin( apply( is_A002113, factor(n)[, 1]))}, [1..9999]) \\ M. F. Hasler, Jan 04 2022

Extensions

Definition clarified by Franklin T. Adams-Watters, Apr 11 2011

Definition simplified by M. F. Hasler, Jan 04 2022