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A082603
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a(n) is the first prime greater than a(n-1) such that a(n)*a(n-1)+2 is a prime, with a(1)=3.
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1
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3, 5, 7, 11, 19, 23, 37, 47, 73, 227, 241, 251, 271, 317, 367, 563, 607, 641, 727, 761, 829, 1091, 1117, 1223, 1249, 1451, 1579, 1601, 1627, 1721, 1741, 1787, 1873, 1877, 1933, 1973, 2017, 2087, 2137, 2153, 2287, 2351, 2521, 2687, 2707, 2741, 2851, 3041, 3121, 3137, 3181, 3191, 3361, 3371, 3457, 3461, 3541, 3557, 3607, 3701, 3877, 3881, 3907, 3947
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| a(3)=7, as 3+2=5, 3*5+2=17, 5*7+2=37, etc.
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MATHEMATICA
| f[s_List] := Block[{p = pp = s[[-1]]}, While[p = NextPrime@p; !PrimeQ[ p*pp + 2], ]; Append[s, p]]; Nest[f, {3}, 63]
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PROG
| (PARI) { vp=vector(20); vp[1]=3; vc=1; vpt=3; print1(3", "); for (vc=2, 20, forprime (p=vp[vc-1]+1, 10000, if (isprime(p*vp[vc-1]+2), vp[vc]=p; vpt*=p; print1(vp[vc]", "); break))) }
(PARI) {v=3; print1(3", "); forprime(p=5, 10000, vp=v*p; if(isprime(vp+2), v=vp; print1(p", ")))} [From Zak Seidov (zakseidov(AT)yahoo.com), Nov 07 2010]
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CROSSREFS
| Cf. A039726, A082603, A096177.
Sequence in context: A138536 A093929 A144427 * A161420 A071997 A093442
Adjacent sequences: A082600 A082601 A082602 * A082604 A082605 A082606
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KEYWORD
| easy,nonn
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AUTHOR
| Jon Perry (perry(AT)globalnet.co.uk), May 23 2003
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EXTENSIONS
| Corrected the definition and example to match the sequence and PARI programming, added the Mathematica coding & two cross references, and extended the sequence Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 08 2010
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