A109031 Numbers that have exactly eleven prime factors counted with multiplicity (A069272) whose digit reversal is different and also has 11 prime factors (with multiplicity).

295245, 426816, 542592, 618624, 2112480, 2116224, 2150064, 2154816, 2196000, 2302560, 2327616, 2342277, 2388672, 2555280, 2576896, 2599200, 2768832, 2952288, 2952576, 4017216, 4074240, 4074840, 4076160, 4076568, 4078848

Offset: 1

Author

Jonathan Vos Post, Jun 16 2005

Keywords

• nonn
• base

Comments

This sequence is the k = 11 instance of the series which begins with k = 1 (emirps), k = 2, k = 3 (A109023), k = 4 (A109024), k = 5 (A109025), k = 6 (A109026), k = 7 (A109027), k = 8 (A109028), k = 9 (A109029), k = 10 (A109030).

Examples

			a(1) = 295245 is in this sequence because 295245 = 3^10 * 5 has exactly 11 prime factors counted with multiplicity and reverse(295245) = 542592 = 2^7 * 3^3 * 157 also has 11 prime factors counted with multiplicity.
		

Links

• David A. Corneth, Table of n, a(n) for n = 1..10000
• Eric Weisstein's World of Mathematics, Almost Prime.
• Eric Weisstein's World of Mathematics, Emirp.
• Eric Weisstein and Jonathan Vos Post, Emirpimes.

Crossrefs

Cf. A069272, A006567, A097393, A109018, A109023, A109024, A109025, A109026, A109027, A109028, A109029, A109030.

Programs

PARI

is(n) = {
	my(r = fromdigits(Vecrev(digits(n))));
	n!=r && bigomega(n) == 11 && bigomega(r) == 11
} \\ David A. Corneth, Mar 07 2024

Extensions

a(5)-a(25) from Donovan Johnson, Apr 09 2010