login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A348050 Palindromes setting a new record of their number of prime divisors A001222. 0
1, 2, 4, 8, 88, 252, 2112, 4224, 8448, 44544, 48384, 405504, 4091904, 405909504, 677707776, 4285005824, 21128282112, 29142024192, 4815463645184, 445488555884544, 27874867776847872, 40539458585493504, 63556806860865536, 840261068860162048, 4870324782874230784 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

MATHEMATICA

m=0; lst=Union@Flatten[Table[{FromDigits@Join[s=IntegerDigits@n, Reverse@s], FromDigits@Join[w=IntegerDigits@n, Rest@Reverse@w]}, {n, 10^5}]]; Do[t=PrimeOmega@lst[[n]]; If[t>m, Print@lst[[n]]; m=t], {n, Length@lst}] (* Giorgos Kalogeropoulos, Oct 25 2021 *)

PROG

(Python)

from sympy import factorint

from itertools import product

def palsthru(maxdigits):

    midrange = [[""], [str(i) for i in range(10)]]

    for digits in range(1, maxdigits+1):

        for p in product("0123456789", repeat=digits//2):

            left = "".join(p)

            if len(left) and left[0] == '0': continue

            for middle in midrange[digits%2]:

                yield int(left+middle+left[::-1])

def afind(maxdigits):

    record = -1

    for p in palsthru(maxdigits):

        f = factorint(p, multiple=True)

        if p > 0 and len(f) > record:

            record = len(f)

            print(p, end=", ")

afind(10) # Michael S. Branicky, Oct 25 2021

CROSSREFS

Cf. A001222, A002113, A046399, A335645.

Cf. A046328, A046329, A046330, A046331, A046332, A046333, A046334, A046335, A046336.

Sequence in context: A322614 A089337 A088114 * A239697 A237913 A076886

Adjacent sequences:  A348047 A348048 A348049 * A348051 A348052 A348053

KEYWORD

nonn,base

AUTHOR

Hugo Pfoertner, Oct 25 2021

EXTENSIONS

a(1) = 1 from David A. Corneth, Oct 25 2021

a(16)-a(19) from Giorgos Kalogeropoulos, Oct 25 2021

a(20) from Michael S. Branicky, Oct 25 2021

a(21)-a(25) from Chai Wah Wu, Oct 28 2021

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 28 20:34 EDT 2022. Contains 357081 sequences. (Running on oeis4.)