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

1,1

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

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A108574 A157931 A338904 * A236108 A253106 A320969

Adjacent sequences: A046365 A046366 A046367 * A046369 A046370 A046371

Keyword

nonn,base

Author

Patrick De Geest, Jun 15 1998

Extensions

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

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

Status

approved