A046396 Palindromes which are the product of 6 distinct primes.

222222, 282282, 474474, 555555, 606606, 646646, 969969, 2040402, 2065602, 2206022, 2417142, 2646462, 2673762, 2875782, 3262623, 3309033, 4179714, 4192914, 4356534, 4585854, 4912194, 5021205, 5169615, 5174715, 5578755

Offset

1,1

Comments

The original definition "Palindromes with exactly 6 distinct prime factors" was misleading. For example, the number 414414 = 2 * 3^2 * 7 * 11 * 13 * 23 has exactly 6 distinct prime factors, although the factor 3 occurs twice. But the listed terms show that it is not in this sequence. See sequence A373466 for the variant corresponding to that definition. - M. F. Hasler, Jun 06 2024

Links

Table of n, a(n) for n=1..25.

Formula

Intersection of A002113 and A067885. - M. F. Hasler, Jun 06 2024

Mathematica

Select[Range[6*10^6], #==IntegerReverse[#]&&PrimeNu[#]==PrimeOmega[#]==6&] (* The program uses the IntegerReverse function from Mathematica version 10 *) (* Harvey P. Dale, Mar 17 2016 *)

Prog

(PARI) A046332_upto(N, start=1, num_fact=6)={ my(L=List()); while(N >= start = nxt_A002113(start), omega(start)==num_fact && issquarefree(start) && listput(L, start)); L} \\ M. F. Hasler, Jun 06 2024

Crossrefs

Cf. A046332 (similar, but for 6 prime factors counted with multiplicity).

Cf. A002113 (palindromes), A067885 (products of 6 distinct primes).

Cf. A074969 (numbers having 6 distinct prime divisors).

Sequence in context: A254516 A254816 A373466 * A083640 A253990 A253997

Adjacent sequences: A046393 A046394 A046395 * A046397 A046398 A046399

Keyword

nonn,base

Author

Patrick De Geest, Jun 15 1998

Extensions

Name edited

Status

approved