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A238257 Numbers n such that n and 2n+1 use only odd decimal digits. 1
1, 3, 5, 7, 9, 15, 17, 19, 35, 37, 39, 55, 57, 59, 75, 77, 79, 95, 97, 99, 155, 157, 159, 175, 177, 179, 195, 197, 199, 355, 357, 359, 375, 377, 379, 395, 397, 399, 555, 557, 559, 575, 577, 579, 595, 597, 599, 755, 757, 759, 775, 777, 779, 795, 797, 799, 955, 957, 959, 975, 977, 979, 995, 997, 999, 1555, 1557, 1559, 1575, 1577, 1579 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Sophie-Germain-analog for numbers with odd digits.

Also numbers with the first digit an odd digit and the other digits in {5, 7, 9}. - David A. Corneth, May 15 2018

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

FORMULA

a(5(3^k-1)/2) = 10^k-1. - Giovanni Resta, Feb 22 2014

MATHEMATICA

Select[Range[1600], AllTrue[Join[IntegerDigits[#], IntegerDigits[ 2#+1]], OddQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, May 15 2018 *)

PROG

(PARI) is(n)=#setminus(setunion(Set(digits(n)), Set(digits(2*n+1))), [1, 3, 5, 7, 9])==0 \\ Charles R Greathouse IV, May 15 2018

CROSSREFS

Cf. A005384, A111153, A211162, A111173, A111176.

Sequence in context: A268496 A121820 A258159 * A305409 A180204 A006995

Adjacent sequences:  A238254 A238255 A238256 * A238258 A238259 A238260

KEYWORD

nonn,base,easy

AUTHOR

Zak Seidov, Feb 21 2014

STATUS

approved

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Last modified February 23 00:18 EST 2019. Contains 320411 sequences. (Running on oeis4.)