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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A046328 Palindromes with exactly 2 prime factors (counted with multiplicity). 13
4, 6, 9, 22, 33, 55, 77, 111, 121, 141, 161, 202, 262, 303, 323, 393, 454, 505, 515, 535, 545, 565, 626, 707, 717, 737, 767, 818, 838, 878, 898, 939, 949, 959, 979, 989, 1111, 1441, 1661, 1991, 3113, 3223, 3443, 3883, 7117, 7447, 7997, 9119, 9229, 9449, 10001 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Zak Seidov and Michael De Vlieger, Table of n, a(n) for n = 1..2816 (First 2000 terms from Zak Seidov)

EXAMPLE

E.g. 111 is a palindrome and 111 = 3*37. 3 and 37 are primes.

MATHEMATICA

fQ[n_] := Block[{id = IntegerDigits[n]}, Plus @@ Last /@ FactorInteger[n] == 2 && id == Reverse[id]]; Select[ Range[ 10000], fQ[ # ] &] (* Robert G. Wilson v, Jun 06 2005 *)

Select[Range[10002], Reverse[x = IntegerDigits[#]] == x && PrimeOmega[#] == 2 &] (* Jayanta Basu, Jun 23 2013 *)

CROSSREFS

Cf. A001358, A046315, A046408, A108505.

Sequence in context: A046338 A118690 A084994 * A196104 A046376 A229129

Adjacent sequences:  A046325 A046326 A046327 * A046329 A046330 A046331

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Jun 15 1998.

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 March 23 04:40 EDT 2017. Contains 283905 sequences.