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A047976 Let (p1,p2), (p3,p4) be pairs of twin primes with p1*p2=p3+p4-1; sequence gives values of p1. 4
5, 11, 41, 71, 599, 641, 881, 2129, 2381, 2687, 3557, 3581, 4547, 6131, 7547, 8009, 9041, 13397, 13931, 15971, 17597, 19139, 21491, 26249, 26261, 34511, 38669, 39227, 39341, 48311, 49739, 52541, 53087, 53591 (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+2, if(q-p==2 && isprime(r=p*q\2) && isprime(r+2), listput(v, p)); 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. A047977-A047979.

Sequence in context: A046121 A023271 A159049 * A006382 A295504 A055113

Adjacent sequences:  A047973 A047974 A047975 * A047977 A047978 A047979

KEYWORD

nonn

AUTHOR

Naohiro Nomoto

STATUS

approved

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Last modified January 29 07:03 EST 2020. Contains 331337 sequences. (Running on oeis4.)