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Smallest prime divisor of (A177941(n))^2-4.
2

%I #9 Dec 14 2018 06:06:28

%S 3,3,7,13,5,3,5,3,37,7,79,7,163,5,3,5,3,11,3,349,17,3,5,3,5,3,17,3,5,

%T 3,5,3,757,17,3,5,3,23,3,5,3,1567,13,5,3,5,3,7,3163,5,3,5,3,17,3,5,3,

%U 5,3,23,3,5,3,37,7,17,3,7,23,3,13,7,5,3,5,3,7,11,3,5,3,5,3,6547,7,13099,7,73

%N Smallest prime divisor of (A177941(n))^2-4.

%C Records are in A177945, indices of records in A177943.

%F a(n) = A020639((A177941(n))^2-4) .

%t Differences[NestList[# + FactorInteger[#^2 - 4][[1, 1]] - 1 &, 5, 100]] + 1 (* _Amiram Eldar_, Dec 14 2018 after _Michael De Vlieger_ at A177941 *)

%o (PARI) listap(nn) = {my(va = vector(nn), p); va[1] = 5; for (n=2, nn, p = factor(va[n-1]^2-4)[1,1]; print1(p, ", "); va[n] = va[n-1] + p - 1;);} \\ _Michel Marcus_, Dec 14 2018

%Y Cf. A177941, A023200, A177930, A177929.

%K nonn

%O 1,1

%A _Vladimir Shevelev_, May 15 2010

%E Entries checked by _R. J. Mathar_, Jun 30 2010