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A276509 Numbers n in base 10 such that the digits of 2 + n are the digits of 2n written in reverse order. 0
2, 47, 497, 4997, 49997, 499997, 4999997, 49999997, 499999997, 4999999997, 49999999997, 499999999997, 4999999999997, 49999999999997, 499999999999997, 4999999999999997, 49999999999999997, 499999999999999997, 4999999999999999997, 49999999999999999997, 499999999999999999997 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..21.

FORMULA

a(n) = 5 * 10^(n - 1) - 3. - Peter Bala, Sep 06 2016

G.f.: (2 + 25*x)/(1 - 11*x + 10*x^2). - Michael De Vlieger, Sep 06 2016

EXAMPLE

47 is in the sequence because 47 + 2 = 49 and 47*2 = 94.

497 is in the sequence because 497 + 2 = 499 and 497*2 = 994.

MATHEMATICA

Select[Range[10^6], IntegerDigits[# + 2] == Reverse@ IntegerDigits[2 #] &] (* or *)

Table[5 (10^(n - 1)) - 3, {n, 22}] (* or *)

CoefficientList[Series[(2 + 25 x)/(1 - 11 x + 10 x^2), {x, 0, 21}], x] (* or *)

{2}~Join~Table[FromDigits@ Join[{4}, ConstantArray[9, {n - 2}], {7}], {n, 2, 22}] (* Michael De Vlieger, Sep 06 2016 *)

PROG

(PARI) isok(n) = digits(n+2) == Vecrev(digits(2*n)); \\ Michel Marcus, Sep 07 2016

(MAGMA) [5*10^(n-1)-3: n in [1..25]]; // Vincenzo Librandi, Sep 09 2016

CROSSREFS

Sequence in context: A128822 A226420 A160922 * A120050 A112783 A277655

Adjacent sequences:  A276506 A276507 A276508 * A276510 A276511 A276512

KEYWORD

nonn,base

AUTHOR

Debapriyay Mukhopadhyay, Sep 06 2016

STATUS

approved

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Last modified April 20 06:19 EDT 2019. Contains 322294 sequences. (Running on oeis4.)