OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..2000
FORMULA
a(k) = p(n+1) - p(n), if n=1, or p(n+1) - p(n) is k-semiprime.
EXAMPLE
a(27)=10 since prime(69)-prime(68)=347-337=10.
MAPLE
L:=[]: cnt:=0; for z to 1 do for k from 1 to 200 do p:=ithprime(k); q:=nextprime(p); x:=q-p; if not(isprime(x)) and numtheory[issqrfree](x) then cnt:=cnt+1; L:=[op(L), [cnt, k, x]] fi od od; L;
MATHEMATICA
Select[Differences[Prime[Range[300]]], !PrimeQ[#]&&SquareFreeQ[#]&] (* Harvey P. Dale, May 07 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Walter Kehowski, Jan 08 2006
STATUS
approved