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Least number m such that 4*m^2 + 1 is prime and the next prime of this form is 4*(m + A214518(n))^2 + 1.
2

%I #7 Aug 06 2012 19:47:49

%S 1,3,13,20,47,92,175,248,1695,1768,22685,41367,49532,178582,420452,

%T 1940278,13957468,20258760

%N Least number m such that 4*m^2 + 1 is prime and the next prime of this form is 4*(m + A214518(n))^2 + 1.

%t n = 1; last = 1; t = {1}; t2 = {1}; While[Length[t] < 10, n++; p = 1 + 4 n^2; If[PrimeQ[p], If[n - last > t[[-1]], AppendTo[t, n - last]; AppendTo[t2, last]]; last = n]]; t2

%Y Cf. A121326 (primes of the form 1+4*n^2), A214517, A214518 (record differences).

%K nonn,hard,more

%O 1,2

%A _T. D. Noe_, Aug 06 2012