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 A248704 Smallest prime such that the n preceding prime gaps are strictly decreasing and the n subsequent prime gaps strictly increasing. 4
 3, 19, 1429, 25243, 340577, 1107791 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..6. Abhiram R Devesh, Python code for generating strict valley primes EXAMPLE a(3)=1429 is in the middle of the sequence of successive primes [1409, 1423, 1427, 1429, 1433, 1439 , 1447] which have prime gaps [14, 4, 2, 4, 6, 8], and 14>4>2 is strictly decreasing and 4<6<8 is strictly increasing. MAPLE A248704 := proc(n) local glist, p, wrks, s ; if n = 0 then return ; else s := n+1 ; p := ithprime(s) ; glist := [seq(ithprime(i+1)-ithprime(i), i=1..2*n)] ; while true do wrks := true; for i from 1 to n-1 do if glist[i] <= glist[i+1] then wrks := false; break; end if; end do: if wrks then for i from n+1 to 2*n-1 do if glist[i] >= glist[i+1] then wrks := false; break; end if; end do: end if; if wrks then return p; end if; p := nextprime(p) ; s := s+1 ; glist := subsop(1=NULL, glist) ; glist := [op(glist), ithprime(s+n)-ithprime(s+n-1)] ; end do: end if; end proc: # R. J. Mathar, Dec 04 2014 CROSSREFS Cf. A248701, A248702, A248703. Sequence in context: A258669 A192340 A326973 * A098796 A365579 A120563 Adjacent sequences: A248701 A248702 A248703 * A248705 A248706 A248707 KEYWORD nonn,more AUTHOR Abhiram R Devesh, Oct 12 2014 STATUS approved

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Last modified June 15 00:47 EDT 2024. Contains 373402 sequences. (Running on oeis4.)