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 A122171 Smallest number m such that there are exactly n primes of form m+p for primes p<2m. 1

%I

%S 1,4,6,10,12,18,38,74,40,24,68,30,36,54,72,100,134,78,60,66,102,96,84,

%T 114,238,90,132,266,126,220,368,174,156,120,150,380,204,180,222,258,

%U 288,276,682,234,530,264,324,252,306,240,490,210,372,270,402,728,408,650

%N Smallest number m such that there are exactly n primes of form m+p for primes p<2m.

%C First occurrence of n in A122170.

%e a(4)=10 because it is the first followed by 14,16,... such that exactly 4 primes p respectively below 2*10,2*14,2*16,... form 4 other primes respectively of form p+10,p+14,p+16,...[For m=10, the 4 primes below 20 are 3,7,13,19 ; For m=14, the 4 primes below 28 are 3,5,17,23 ; For m=16, the 4 primes below 32 are 3,7,13,31 ; ...]

%p A122171 := proc(n) local m,p,pgood; m := 0 ; while true do p := 2 ; pgood := 0 ; while p <= 2*m do if isprime(m+p) then pgood := pgood+1 ; fi ; p := nextprime(p) ; od ; if pgood = n then RETURN(m) ; fi ; m := m+1 ; od ; end: for n from 1 to 80 do printf("%d, ",A122171(n)) ; od : # _R. J. Mathar_, Dec 16 2006

%K nonn

%O 1,2

%A _Lekraj Beedassy_, Aug 23 2006

%E More terms from _R. J. Mathar_, Dec 16 2006

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Last modified September 22 03:54 EDT 2020. Contains 337289 sequences. (Running on oeis4.)