login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A154545 Odd nonprimes k such that the smallest digit of k + the number of smallest digits of k is prime. 1
1, 15, 21, 25, 27, 33, 45, 49, 51, 55, 69, 81, 91, 99, 115, 117, 119, 121, 123, 125, 129, 133, 135, 141, 143, 145, 147, 153, 155, 159, 161, 165, 169, 171, 175, 177, 183, 185, 187, 189, 195, 213, 215, 217, 219, 221, 231, 235, 237, 243, 245, 247, 249, 253, 255 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Jinyuan Wang, Table of n, a(n) for n = 1..10000

EXAMPLE

1 is the smallest digit of 15 and it appears once, 1+1 is prime so 15 appears in the sequence; and so does 21, 51, 81, 91.

MAPLE

frequdig := proc(n, dig) local f, d ; f := 0 ; for d in convert(n, base, 10) do if d = dig then f :=f+1; end if; end do; f ; end proc:

A054054 := proc(n) min(op(convert(n, base, 10)) ) ; end proc:

for n from 1 to 500 by 2 do if not isprime(n) then sdg := A054054(n) ; a := sdg +frequdig(n, sdg) ; if isprime(a) then printf("%d, ", n ) ; end if; end if; end do: # R. J. Mathar, May 05 2010

CROSSREFS

Cf. A054054 (smallest digit of n).

Sequence in context: A306102 A177024 A325037 * A156063 A181780 A273061

Adjacent sequences: A154542 A154543 A154544 * A154546 A154547 A154548

KEYWORD

nonn,base,less

AUTHOR

Juri-Stepan Gerasimov, Jan 11 2009

EXTENSIONS

Entries checked by R. J. Mathar, May 05 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 4 09:27 EST 2022. Contains 358556 sequences. (Running on oeis4.)