OFFSET
1,1
COMMENTS
Primes p such that p = sum of n-th and (n+1)-st semiprimes for some n.
Primes appearing in A109404.
LINKS
Zak Seidov, Table of n, a(n) for n = 1..10000
EXAMPLE
19 = sp(3) + sp(4) = 9 + 10 where sp(n) = n-th semiprime.
29 is a member because 2*7 + 3*5 = 29.
13 is not a member because although 2*2 + 3*3 = 13, 4 and 9 are not successive semiprimes.
MATHEMATICA
Select[ Plus @@@ Partition[ Select[ Range[1250], Plus @@ Last /@ FactorInteger[ # ] == 2 &], 2, 1], PrimeQ[ # ] &] (* Robert G. Wilson v, Jun 14 2005 *)
Select[Total/@Partition[Select[Range[1500], PrimeOmega[#]==2&], 2, 1], PrimeQ] (* Harvey P. Dale, Nov 15 2013 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Giovanni Teofilatto, Jun 14 2005
EXTENSIONS
Corrected and extended by Robert G. Wilson v, Jun 14 2005
Edited by N. J. A. Sloane, May 03 2007
STATUS
approved