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A176539
Indices of nonprime numbers in the products of two noncomposite numbers.
1
1, 4, 6, 8, 9, 12, 13, 16, 17, 19, 20, 23, 24, 25, 27, 28, 31, 33, 34, 36, 37, 38, 41, 42, 44, 47, 48, 50, 52, 53, 54, 56, 57, 58, 59, 63, 66, 68, 69, 70, 71, 72, 73, 75, 77, 78, 81, 82, 83, 84, 85, 88, 90, 91, 92, 94, 96, 98, 99, 102, 103, 104, 107, 110, 111, 112, 113, 114
OFFSET
1,2
COMMENTS
The positions of nonprime numbers in A037143.
The nonprime numbers A018252 which are not in A037143 do not contribute to the sequence and have no index of this kind. - R. J. Mathar, May 01 2010
MAPLE
From R. J. Mathar, May 01 2010: (Start)
A037143 := 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:
A018252 := proc(n) option remember; if n = 1 then 1; else for a from procname(n-1)+1 do if not isprime(a) then return a; end if; end do: end if; end proc:
A176539 := proc(n) npr := A018252(n) ; for a from 1 do if A037143(a) = npr then return a ; elif A037143(a) > npr then return ; end if; end do: end proc: seq(A176539(n), n=1..220) ; (End)
CROSSREFS
Cf. A018252.
Sequence in context: A338461 A163520 A273546 * A285256 A013920 A179891
KEYWORD
nonn
AUTHOR
EXTENSIONS
Corrected (70 inserted) by R. J. Mathar, May 01 2010
STATUS
approved