A176807 Lesser of twin primes p such that p = semiprime(k)/3 and p + 2 = semiprime(k+3)/3 for some integer k.

3, 107, 137, 179, 239, 419, 461, 659, 1049, 1091, 1697, 1787, 1871, 2027, 2111, 2381, 2687, 2711, 3167, 3299, 3329, 3359, 3371, 3467, 3851, 4259, 4721, 4967, 5279, 5501, 5639, 5651, 5867, 6269, 6449, 7487, 8819, 8969, 9011, 9431, 9629

Offset

1,1

Links

Table of n, a(n) for n=1..41.

Example

3 is a term because 3 = semiprime(3)/3 = 9/3 and 3 + 2 = 5 = semiprime(3+3)/3 = 15/3.

Maple

From R. J. Mathar, Apr 27 2010: (Start)
isA001358 := proc(n) numtheory[bigomega](n) = 2 ; end proc:
A001358 := proc(n) option remember ; if n = 1 then 4; else for a from procname(n-1)+1 do if isA001358(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:
A001359 := proc(n) option remember; if n = 1 then 3; else for a from procname(n-1)+2 by 2 do if isprime(a) and isprime(a+2) then return a; end if; end do: end if; end proc:
for i from 1 to 200 do p := A001359(i) ; n := A174956(3*p) ; n3 := A174956(3*p+6) ; if n > 0 and n3 >0 and n3=n+3 then printf("%d, ", p) ; end if; end do: (End)

Crossrefs

Sequence in context: A213862 A245657 A139921 * A301369 A142509 A023325

Adjacent sequences: A176804 A176805 A176806 * A176808 A176809 A176810

Keyword

nonn

Author

Juri-Stepan Gerasimov, Apr 26 2010

Extensions

Corrected (659 inserted, 1031 removed, 2027 inserted) and extended by R. J. Mathar, Apr 27 2010

Status

approved