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!)
A281625 Numbers n>0 such that n = k*(reversal of k*n) for some k<=n. 2
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 20, 22, 30, 33, 40, 44, 50, 55, 60, 66, 70, 77, 80, 88, 90, 99, 100, 101, 110, 111, 121, 131, 141, 151, 161, 171, 181, 191, 200, 202, 212, 220, 222, 232, 242, 252, 262, 272, 282, 292, 300, 303, 313, 323, 330, 333, 343, 353 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Generalisation of palindrome numbers in base 10.

Sequence is not the same as A061917 or A169824; a(188) = 3267 is not term of these sequences.

Supersequence of A002113 (palindromes in base 10) and A061917.

Sequences a(n)_k of numbers m such that m = k*(reversal of k*m) for k <= 30 and n >= 1:

a(n)_1 = A002113(n+1) (palindromes > 0 in base 10);

a(n)_2 = 4356, 43956, 439956, 4399956, 43999956, 439999956, ...;

a(n)_3 = 3267, 32967, 329967, 3299967, 32999967, 329999967, ...;

a(n)_5 = a(n)_20 = 10*a(n)_2 = 43560, 439560, 4399560, 43999560, ...;

a(n)_8 = 6600, 6606600, 66006600, 660006600, ...;

a(n)_10 = 10*A002113(n+1): 10, 20, 30, 40, 50, 60, 70, 80, 90, 110, ... ;

a(n)_30 = 10*a(n)_3 = 32670, 329670, 3299670, 32999670, ...

LINKS

Jaroslav Krizek, Table of n <= 5000

EXAMPLE

3267 is in the sequence because 3267 = 3*(reversal of 3*3267) = 3*(reversal of 9801) = 3*1089.

MAPLE

read("transforms") :

isA281625 := proc(n)

    for k from 1 to n do

        if k*digrev(k*n) = n then

            return true ;

        end if;

    end do:

    false;

end proc:

A281625 := proc(n)

    option remember ;

    if n = 1 then

        1;

    else

        for a from procname(n-1)+1 do

            if isA281625(a) then

                return a;

            end if;

        end do:

    end if;

end proc:

seq(A281625(n), n=1..100) ; # R. J. Mathar, Aug 06 2019

MATHEMATICA

Select[Range@ 353, Function[n, Total@ Boole@ Map[Function[k, n == k FromDigits@ Reverse[IntegerDigits[k n]]], Range@ n] > 0]] (* Michael De Vlieger, Feb 11 2017 *)

PROG

(MAGMA) [n: k in [1..n], n in [1..1000] | n eq k * Seqint(Reverse(Intseq(k*n)))]

CROSSREFS

Cf. A061917, A002113, A169824.

Sequence in context: A061362 A096091 A084050 * A169824 A325152 A061917

Adjacent sequences:  A281622 A281623 A281624 * A281626 A281627 A281628

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Feb 11 2017

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 10 08:22 EDT 2020. Contains 336368 sequences. (Running on oeis4.)