login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A109026 6-almost primes (A046306) whose digit reversal is different and also has 6 prime factors (with multiplicity). "Emirp Tsolma-6.". 8
2576, 2970, 4284, 4356, 4410, 4600, 4698, 4824, 5265, 5625, 6534, 6752, 6900, 8250, 8964, 10710, 10890, 13140, 13986, 16236, 16335, 17577, 18504, 19494, 20286, 20574, 21114, 21150, 21160, 21336, 21492, 21576, 21609, 21900, 21996, 22392, 22770 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This sequence is the k = 6 instance of the series which begins with k = 1 (emirps), k = 2 (emirpimes), k = 3 (emirp tsolma-3 = A109023), k = 4 (emirp tsolma-4 = A109024), k = 5 (emirp tsolma-5 = A109025).

The Mathematica code for this was written by Ray Chandler who extended this sequence. He also has more values.

REFERENCES

Jonathan Vos Post, "1066 and All That: Emirp Tsolma-3 and Related Integer Sequences." Forthcoming paper on this sequence.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..3500

Eric Weisstein's World of Mathematics, Almost Prime.

Eric Weisstein's World of Mathematics, Emirp.

Eric Weisstein and Jonathan Vos Post, Emirpimes.

EXAMPLE

a(1) = 2576 is in this sequence because 2576 = 2^4 * 7 * 23 is a 6-almost prime and reverse(2576) = 6752 = 2^5 * 211 is also a 6-almost prime.

MATHEMATICA

Select[Range[23000], !PalindromeQ[#]&&Total[FactorInteger[#][[All, 2]]] == Total[FactorInteger[IntegerReverse[#]][[All, 2]]]==6&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Oct 10 2017 *)

CROSSREFS

Cf. A046306, A006567, A097393, A109018, A109023-A109025, A109027-A109131.

Sequence in context: A260104 A031789 A001294 * A217183 A034415 A201510

Adjacent sequences:  A109023 A109024 A109025 * A109027 A109028 A109029

KEYWORD

nonn,base

AUTHOR

Jonathan Vos Post, Jun 16 2005

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 11 00:32 EDT 2020. Contains 336403 sequences. (Running on oeis4.)