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

Offset: 0

Author

Michel Lagneau, Aug 02 2012

Keywords

• nonn

Comments

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

Examples

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

Crossrefs

Cf. A007921.

Programs

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: