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 A218209 Number of n-digit primes that are of the form (k-2)^2 + (k-1)^2 + k^2 4
 2, 1, 3, 4, 12, 31, 86, 230, 681, 1934, 5634, 15772 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS FORMULA a(n) = A218210(n) - A218210(n-1) MATHEMATICA n = -1; Table[cnt = 0; While[n++; p = 3*n^2 + 2; p < 10^e, If[PrimeQ[p], cnt++]]; n--; cnt, {e, 10}] (* T. D. Noe, Oct 23 2012 *) Table[Count[Table[Total[Range[n, n+2]^2], {n, -1, 600000}], _?(PrimeQ[#] && IntegerLength[#]==k&)], {k, 12}] (* Harvey P. Dale, Oct 17 2016 *) CROSSREFS Cf. A027863, A027864, A218207, A218210, A218211. Sequence in context: A052950 A086851 A001054 * A141487 A217103 A099866 Adjacent sequences:  A218206 A218207 A218208 * A218210 A218211 A218212 KEYWORD nonn,base AUTHOR Martin Renner, Oct 23 2012 STATUS approved

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Last modified April 3 22:48 EDT 2020. Contains 333207 sequences. (Running on oeis4.)