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A217222
Initial terms of sets of 8 consecutive semiprimes with gap 2.
2
8129, 237449, 401429, 452639, 604487, 858179, 1471727, 1999937, 2376893, 2714987, 3111977, 3302039, 3869237, 4622087, 7813559, 9795449, 10587899, 10630739, 11389349, 14186387, 14924153, 15142547, 15757337, 18017687, 18271829, 19732979, 22715057, 25402907
OFFSET
1,1
COMMENTS
All terms == 11 (mod 18).
Also all terms of sets of 8 consecutive semiprimes are odd, e.g., {8129, 8131, 8133, 8135, 8137, 8139, 8141, 8143} is the smallest set of 8 consecutive semiprimes.
Note that in all cases "9th term" (in this case 8143+2=8145) is divisible by 9 and hence is not semiprime.
Also note that all seven "intermediate" even integers (in this case {8130, 8132, 8134, 8136, 8138, 8140, 8142}) have at least three prime factors counting with multiplicity. Up to n = 40*10^9 there are 5570 terms of this sequence.
MATHEMATICA
Transpose[Select[Partition[Select[Range[26*10^6], PrimeOmega[#] == 2&], 8, 1], Union[ Differences[#]]=={2}&]][[1]] (* Harvey P. Dale, Sep 02 2015 *)
CROSSREFS
Subsequence of A082919.
Sequence in context: A088846 A092208 A082919 * A252144 A201802 A233814
KEYWORD
nonn
AUTHOR
Zak Seidov, Sep 28 2012
STATUS
approved