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A058620 Lesser of two consecutive primes whose difference divided by two is a prime: ( prime(next prime after n) - prime(n) )/2 is prime. 3
7, 13, 19, 23, 31, 37, 43, 47, 53, 61, 67, 73, 79, 83, 97, 103, 109, 113, 127, 131, 139, 151, 157, 163, 167, 173, 181, 193, 223, 229, 233, 241, 251, 257, 263, 271, 277, 283, 293, 307, 313, 317, 331, 337, 349, 353, 367, 373, 379, 383, 397, 409, 421, 433, 439 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Lesser of two consecutive primes whose difference is a semiprime (A001358). - Zak Seidov, Nov 19 2016

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

MATHEMATICA

Do[ If[ PrimeQ[ (Prime[n + 1] - Prime[n] )/2], Print[ Prime[n] ]], {n, 1, 100} ]

p=7; Reap[Do[If[PrimeQ[((q=NextPrime[p])-p)/2], Sow[p]]; p=q, {100}]][[2, 1]] (* Zak Seidov, Nov 19 2016 *)

Select[Partition[Prime[Range[100]], 2, 1], PrimeQ[(#[[2]]-#[[1]])/2]&][[All, 1]] (* Harvey P. Dale, Jan 20 2021 *)

PROG

(PARI) isok(p) = isprime(p) && isprime((nextprime(p+1) - p)/2); \\ Michel Marcus, Nov 19 2016

(PARI) v=List(); p=3; forprime(q=5, , if(isprime((q-p)/2), listput(v, p); if(#v==10^4, return)); p=q) \\ Charles R Greathouse IV, Nov 20 2016

CROSSREFS

Cf. A001358.

Sequence in context: A049591 A176180 A209623 * A038910 A035497 A216527

Adjacent sequences:  A058617 A058618 A058619 * A058621 A058622 A058623

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Dec 28 2000

STATUS

approved

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Last modified June 12 12:53 EDT 2021. Contains 344947 sequences. (Running on oeis4.)