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Number of n-digit primes of the form (k-1)^2 + k^2.
4

%I #8 Oct 23 2012 13:18:40

%S 1,3,6,16,42,107,286,764,2124,5917,17250,49818,145429

%N Number of n-digit primes of the form (k-1)^2 + k^2.

%F a(n) = A218208(n) - A218208(n-1)

%t n = 0; Table[cnt = 0; While[n++; p = 2*n^2 - 2*n + 1; p < 10^e, If[PrimeQ[p], cnt++]]; n--; cnt, {e, 10}] (* _T. D. Noe_, Oct 23 2012 *)

%Y Cf. A027861, A027862, A218208, A218209, A218211.

%K nonn,base

%O 1,2

%A _Martin Renner_, Oct 23 2012