A176512 Indices of products of 2 single (or isolated or non-twin) primes in the semiprimes.

1, 16, 25, 33, 35, 45, 52, 55, 58, 62, 76, 82, 84, 100, 104, 107, 111, 133, 137, 143, 155, 158, 162, 164, 174, 183, 188, 194, 198, 202, 214, 218, 222, 225, 229, 231, 234, 241, 243, 249, 257, 263, 265, 269, 274, 281, 287, 292, 294, 299, 301, 304, 319, 320, 321

Offset

1,2

Links

Table of n, a(n) for n=1..55.

Formula

A001358(k) = A176312(a(n)).

a(n) = A174956(A176312(n)). - R. J. Mathar, May 02 2010

Maple

From R. J. Mathar, May 02 2010: (Start)
isA007510 := proc(n) isprime(n) and not isprime(n+2) and not isprime(n-2) ; simplify(%) ; end proc:
isA176312 := proc(n) for d in numtheory[divisors](n) do if isA007510(d) and isA007510(n/d) then return true; end if; end do: return false; end proc:
A176312 := proc(n) option remember; if n = 1 then 4; else for a from procname(n-1)+1 do if isA176312(a) then return a; end if; end do: end if; end proc:
A174956 := proc(p) option remember ; for n from 1 do if A001358(n) = p then return n; elif A001358(n) > p then return 0 ; end if; end do: end proc:
A176512 := proc(n) A174956(A176312(n)) ; end proc:
seq(A176512(n), n=1..120) ; (End)

Crossrefs

Sequence in context: A111026 A124186 A274240 * A001033 A100647 A245371

Adjacent sequences: A176509 A176510 A176511 * A176513 A176514 A176515

Keyword

nonn

Author

Juri-Stepan Gerasimov, Apr 19 2010

Extensions

Entries checked by R. J. Mathar, May 02 2010

Status

approved