A215081 - OEIS

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.

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

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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: A297574 A349984 A375005 * A348592 A337737 A119416

Adjacent sequences: A215078 A215079 A215080 * A215082 A215083 A215084

KEYWORD

nonn

AUTHOR

Michel Lagneau, Aug 02 2012

STATUS

approved