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!)
A284294 Numbers using only digits 1 and 9. 3
1, 9, 11, 19, 91, 99, 111, 119, 191, 199, 911, 919, 991, 999, 1111, 1119, 1191, 1199, 1911, 1919, 1991, 1999, 9111, 9119, 9191, 9199, 9911, 9919, 9991, 9999, 11111, 11119, 11191, 11199, 11911, 11919, 11991, 11999, 19111, 19119, 19191, 19199, 19911, 19919 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Product of digits of n is a power of 9; subsequence of A284295.

Prime terms are in A020457.

LINKS

Table of n, a(n) for n=1..44.

FORMULA

The sum of first 2^n terms is (5*20^n + 38*10^n - 95*2^n + 1420)/171. Giovanni Resta, Mar 25 2017

MATHEMATICA

Join @@ (FromDigits /@ Tuples[{1, 9}, #] & /@ Range[5]) (* Giovanni Resta, Mar 25 2017 *)

PROG

(MAGMA) [n: n in [1..20000] | Set(IntegerToSequence(n, 10)) subset {1, 9}]

CROSSREFS

Cf. Numbers using only digits 1 and k for k = 0 and k = 2 - 9: A007088 (k = 0), A007931 (k = 2), A032917 (k = 3), A032822 (k = 4) , A276037 (k = 5), A284293 (k = 6), A276039 (k = 7), A213084 (k = 8), this sequence (k = 9).

Sequence in context: A090771 A329279 A284295 * A195572 A046259 A258452

Adjacent sequences:  A284291 A284292 A284293 * A284295 A284296 A284297

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Mar 25 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 February 27 06:36 EST 2020. Contains 332299 sequences. (Running on oeis4.)