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A176807 Lesser of twin primes p such that p = semiprime(k)/3 and p + 2 = semiprime(k+3)/3 for some integer k. 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified June 16 05:18 EDT 2019. Contains 324145 sequences. (Running on oeis4.)