OFFSET
1,1
COMMENTS
Semiprimes in arithmetic progression. All terms are odd, see also A056809.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
MATHEMATICA
PrimeFactorExponentsAdded[n_] := Plus @@ Flatten[Table[ #[[2]], {1}] & /@ FactorInteger[n]]; Select[ Range[ 4626], PrimeFactorExponentsAdded[ # ] == PrimeFactorExponentsAdded[ # + 2] == PrimeFactorExponentsAdded[ # + 4] == PrimeFactorExponentsAdded[ # + 6] == 2 &] (* Robert G. Wilson v, Feb 24 2004 *)
Transpose[SequencePosition[Table[If[PrimeOmega[n]==2, 1, 0], {n, 5000}], {1, _, 1, _, 1, _, 1}]][[1]] (* The program uses the SequencePosition function from Mathematica version 10 *) (* Harvey P. Dale, Feb 10 2016 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Zak Seidov, Feb 22 2004
STATUS
approved