login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons 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 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A215081 Smallest number k such that the difference between the greatest prime divisor and the smallest prime divisor of k equals n,  or 0 if there is no such k. 0
2, 6, 15, 10, 21, 14, 55, 0, 33, 22, 39, 26, 85, 0, 51, 34, 57, 38, 115, 0, 69, 46, 203, 0, 145, 0, 87, 58, 93, 62, 259, 0, 185, 0, 111, 74, 205, 0, 123, 82, 129, 86, 235, 0, 141, 94, 371, 0, 265, 0, 159, 106, 413, 0, 295, 0, 177, 118, 183, 122, 469, 0, 335, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

a(A007921(n)) = 0 where A007921(n) are the numbers that are not the difference of two primes.

LINKS

Table of n, a(n) for n=0..63.

EXAMPLE

a(2) = 15 because 15 = 3*5 and 5 - 3 = 2.

MAPLE

with(numtheory):for n from 0 to 65 do:ii:=0:for k from 2 to 10000 while(ii=0) do:x:=factorset(k):n1:=nops(x):d:=x[n1] - x[1]:if d=n then ii:=1: printf("%a, ", k):else fi:od:if ii=0 then printf("%a, ", 0):else fi:od:

CROSSREFS

Cf. A007921.

Sequence in context: A130642 A133933 A297574 * A337737 A119416 A134891

Adjacent sequences:  A215078 A215079 A215080 * A215082 A215083 A215084

KEYWORD

nonn

AUTHOR

Michel Lagneau, Aug 02 2012

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 November 30 05:11 EST 2021. Contains 349418 sequences. (Running on oeis4.)