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 A082603 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. 1
 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; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE a(3)=7, as 3 + 2 = 5, 3*5 + 2 = 17, 5*7 + 2 = 37, etc. MATHEMATICA f[s_List] := Block[{p = pp = s[[-1]]}, While[p = NextPrime@p; !PrimeQ[ p*pp + 2], ]; Append[s, p]]; Nest[f, {3}, 63] (* Robert G. Wilson v, Nov 08 2010 *) 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", ")))} \\ Zak Seidov, Nov 07 2010 CROSSREFS Cf. A039726, A082603, A096177. Sequence in context: A138536 A093929 A144427 * A161420 A071997 A093442 Adjacent sequences:  A082600 A082601 A082602 * A082604 A082605 A082606 KEYWORD easy,nonn AUTHOR Jon Perry, May 23 2003 EXTENSIONS Definition and example corrected to match the sequence and PARI programming, two cross references added, and sequence extended by Robert G. Wilson v, Nov 08 2010 STATUS approved

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Last modified August 8 05:25 EDT 2020. Contains 336290 sequences. (Running on oeis4.)