A162357 - OEIS

%I #14 Feb 25 2019 10:47:24

%S 29,43,61,89,1021,1201,1409,16111,18233,20369,220447,24709,26267,

%T 28123,30727,320867,34549,360461,38393,404557,421517,444209,465841,

%U 481249,5000423,521929,540907,565667,58831,605719,6217319,6403063,6611237

%N a(n) is the smallest prime p beginning with 2n such that the difference between p and the next prime is 2n.

%e 29 is a member since the next prime is 31, 31 - 29 = 2, and 29 begins with 2.

%e 18233 is the smallest prime that begins with 18 and is followed by an 18-gap.

%p A162357 := proc(n) local a,b,p; a := 2*n; for d from 1 do for b from 1 to 10^d by 2 do p := a*10^d+b ; if isprime(p) then if nextprime(p)-p = 2*n then RETURN(p) ; fi; fi; od: od: end: for n from 1 do printf("%d,\n",A162357(n)) ; od: # _R. J. Mathar_, Jul 06 2009

%K base,nonn

%O 1,1

%A _Ki Punches_, Jul 01 2009

%E Edited by _N. J. A. Sloane_, Jul 05 2009

%E Extended by _Ray Chandler_, Jul 08 2009

%E 1237 replaced by 1201 and extended beyond a(24) by _R. J. Mathar_, Jul 06 2009

%E Definition modified by _Harvey P. Dale_, Jan 24 2019