A162357 a(n) is the smallest prime p beginning with 2n such that the difference between p and the next prime is 2n.

29, 43, 61, 89, 1021, 1201, 1409, 16111, 18233, 20369, 220447, 24709, 26267, 28123, 30727, 320867, 34549, 360461, 38393, 404557, 421517, 444209, 465841, 481249, 5000423, 521929, 540907, 565667, 58831, 605719, 6217319, 6403063, 6611237

Offset

1,1

Links

Table of n, a(n) for n=1..33.

Example

29 is a member since the next prime is 31, 31 - 29 = 2, and 29 begins with 2.
18233 is the smallest prime that begins with 18 and is followed by an 18-gap.

Maple

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

Crossrefs

Sequence in context: A168474 A341666 A247896 * A316741 A173967 A004619

Adjacent sequences: A162354 A162355 A162356 * A162358 A162359 A162360

Keyword

base,nonn

Author

Ki Punches, Jul 01 2009

Extensions

Edited by N. J. A. Sloane, Jul 05 2009

Extended by Ray Chandler, Jul 08 2009

1237 replaced by 1201 and extended beyond a(24) by R. J. Mathar, Jul 06 2009

Definition modified by Harvey P. Dale, Jan 24 2019

Status

approved