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!)
A192130 Numbers n such that n divided by the number constructed from a decimal point followed by the reversed digits of n is an integer, but not a power of ten. 1
21, 42, 51, 52, 54, 57, 63, 81, 84, 210, 231, 270, 297, 420, 462, 510, 520, 521, 522, 528, 540, 561, 570, 572, 573, 594, 610, 630, 693, 810, 840, 861, 891, 2100, 2121, 2178, 2300, 2310, 2331, 2530, 2541, 2700, 2727, 2751, 2961, 2970, 2997, 4032, 4200, 4242 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Quotients equal to a power of 10 are excluded to eliminate trivial cases, e.g., 777/.777 = 1000.

If n is in this sequence, so is 10*n. However, 10*n can be in this sequence even if n is not (e.g., 270 is in the sequence even though 27 is not). - Nathaniel Johnston, Jun 23 2011

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 1..750

EXAMPLE

a(1) = 21 because 21/.12 = 175;

a(6) = 57 because 57/.75 = 76.

MAPLE

isA192130 := proc(n) local d, m: d:=convert(n, base, 10): m:=n/add(d[j]*10^(-j), j=1..nops(d)): return `if`(type(m, integer) and not type(simplify(log[10](m)), integer), n, NULL): end: seq(isA192130(n), n=1..4410); # Nathaniel Johnston, Jun 23 2011

MATHEMATICA

revRec[n_, b_:10] := FromDigits[Reverse[IntegerDigits[n, b]]]/b^Length[IntegerDigits[n, b]]; Select[Range[3000], IntegerQ[#/revRec[#]] && Not[IntegerQ[Log[10, #/revRec[#]]]] &] (* Alonso del Arte, Jun 23 2011 *)

CROSSREFS

Sequence in context: A120772 A260749 A040420 * A258188 A037978 A089059

Adjacent sequences:  A192127 A192128 A192129 * A192131 A192132 A192133

KEYWORD

nonn,base

AUTHOR

Gil Broussard, Jun 23 2011

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 June 18 12:22 EDT 2021. Contains 345104 sequences. (Running on oeis4.)