login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A046368 Numbers with exactly 2 palindromic prime factors (counted with multiplicity), and no other prime factors. 6
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 (list; graph; refs; listen; history; text; internal format)
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.

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 *)

CROSSREFS

Cf. A001358, A046400, A001358.

Sequence in context: A264815 A108574 A157931 * A236108 A253106 A113433

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

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified July 26 08:41 EDT 2017. Contains 289800 sequences.