A046393 Palindromes with exactly 3 distinct prime factors.

66, 222, 282, 434, 474, 494, 555, 595, 606, 646, 777, 969, 1001, 1221, 1551, 1771, 2222, 2882, 3333, 3553, 4334, 4994, 5335, 5555, 5665, 5885, 5995, 6226, 6446, 6886, 7337, 7557, 7667, 7777, 7887, 8338, 8558, 8998, 9339, 9669, 9779, 9889, 11211

Offset

1,1

Comments

The terms must have only three distinct prime factors even when counted with multiplicity. For example, 252 is not a term even though (1) it is a palindrome and (2) only three distinct primes occur when it is factored, because 252 = 2*2*3*3*7. - Harvey P. Dale, Aug 29 2016

Links

Chai Wah Wu, Table of n, a(n) for n = 1..10000

Mathematica

Select[Range[12000], #==IntegerReverse[#]&&PrimeNu[#]==PrimeOmega[#]==3&] (* Harvey P. Dale, Aug 29 2016 *)

Crossrefs

Cf. A046329, A046409.

Sequence in context: A202640 A074873 A205817 * A268582 A117306 A322768

Adjacent sequences: A046390 A046391 A046392 * A046394 A046395 A046396

Keyword

nonn,base

Author

Patrick De Geest, Jun 15 1998

Status

approved