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A047977 Let (p1,p2), (p3,p4) be pairs of twin primes with p1*p2=p3+p4-1; sequence gives values of p2. 2
7, 13, 43, 73, 601, 643, 883, 2131, 2383, 2689, 3559, 3583, 4549, 6133, 7549, 8011, 9043, 13399, 13933, 15973, 17599, 19141, 21493, 26251, 26263, 34513, 38671, 39229, 39343, 48313, 49741, 52543, 53089, 53593, 55051, 55663, 56101 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

E.g. 5*7=17+19-1,11*13=71+73-1.

PROG

(PARI) list(lim)=my(v=List(), p=3, r); forprime(q=5, lim, if(q-p==2 && isprime(r=p*q\2) && isprime(r+2), listput(v, q)); p=q); Vec(v) \\ Charles R Greathouse IV, Sep 29 2015

(PARI) is(n)=isprime(n) && isprime(n-2) && isprime(n*(n-2)\2) && isprime(n*(n-2)\2+2) \\ Charles R Greathouse IV, Sep 29 2015

CROSSREFS

Cf. A047976-A047979.

Sequence in context: A259186 A151781 A224502 * A139403 A087820 A272032

Adjacent sequences:  A047974 A047975 A047976 * A047978 A047979 A047980

KEYWORD

nonn

AUTHOR

Naohiro Nomoto

STATUS

approved

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Last modified August 18 18:11 EDT 2017. Contains 290732 sequences.