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A176650
Numbers k such that nonnegative non-semiprime(k)+3 = nonnegative non-semiprime(k+3).
1
1, 11, 12, 18, 19, 20, 26, 27, 28, 47, 53, 63, 64, 65, 66, 67, 68, 69, 73, 83, 84, 91, 92, 93, 98, 99, 100, 101, 102, 109, 115, 116, 117, 118, 122, 128, 129, 130, 134, 135, 136, 148, 152, 153, 154, 155, 156, 161, 162, 163, 164, 165, 166, 174, 183, 184, 185, 192, 193
OFFSET
1,2
COMMENTS
Where nonnegative non-semiprime numbers are zero together with A100959 (i.e., 0, 1, 2, 3, 5, 7, 8, 11, 12, 13, 16, 17, 18, 19, 20, 23, 24, 27, 28, 29, 30, ...).
LINKS
EXAMPLE
1 is a term because nonnegative non-semiprime(1)+3 = 3 = nonnegative non-semiprime(1+3).
MAPLE
A100959 := proc(n) option remember; if n = 1 then 1; else for a from procname(n-1)+1 do if numtheory[bigomega](a) <> 2 then return a; end if; end do end if; end proc:
nnnspr := proc(n) if n = 1 then 0; else A100959(n-1) ; end if; end proc:
isA176650 := proc(n) nnnspr(n) + 3 = nnnspr(n+3) ; end proc:
for n from 1 to 1200 do if isA176650(n) then printf("%d, ", n) ; end if; end do:
# R. J. Mathar, Apr 26 2010
MATHEMATICA
Join[{1}, Flatten[With[{c=Select[Range[0, 300], PrimeOmega[#]!=2&]}, Position[ Partition [c, 4, 1], _?(#[[1]]+3==#[[4]]&), 1, Heads->False]]]+1] (* Harvey P. Dale, Oct 15 2022 *)
CROSSREFS
Cf. A100959 (non-semiprimes).
Sequence in context: A079350 A070605 A087450 * A046465 A134926 A105744
KEYWORD
nonn
AUTHOR
EXTENSIONS
Entries checked by R. J. Mathar, Apr 26 2010
STATUS
approved