A238257 Numbers n such that n and 2n+1 use only odd decimal digits.

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

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: A357150 A351462 A258159 * A305409 A342572 A359402

Adjacent sequences: A238254 A238255 A238256 * A238258 A238259 A238260

Keyword

nonn,base,easy

Author

Zak Seidov, Feb 21 2014

Status

approved