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 A224870 Numbers n such that n^2 + (n+3)^2 is prime. 1
 1, 2, 5, 7, 10, 11, 16, 20, 22, 25, 37, 40, 41, 46, 50, 55, 61, 62, 65, 77, 85, 91, 92, 101, 106, 107, 116, 122, 125, 127, 130, 131, 142, 145, 146, 152, 155, 161, 172, 181, 182, 187, 196, 197, 206, 220, 221, 232, 235, 241, 242, 257, 260, 262, 265, 271, 275, 280, 281, 286, 295, 310, 317, 325, 326, 346, 356, 362, 380, 382, 386, 391 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Zak Seidov, Table of n, a(n) for n = 1..1000 FORMULA a(n) = (1/2)*(sqrt(2*A076727(n) - k^2) - k), k = 3. MAPLE A224870:=n->`if`(isprime(n^2 + (n+3)^2), n, NULL): seq(A224870(n), n=1..10^3); # Wesley Ivan Hurt, Feb 11 2017 MATHEMATICA k = 3; Select[Range[500], PrimeQ[#^2 + (# + k)^2]&] PROG (PARI) isok(n) = isprime(n^2 + (n+3)^2)); \\ Michel Marcus, Feb 13 2017 CROSSREFS Cf. A027861, A027862, A076727. Sequence in context: A049842 A018636 A068007 * A033094 A206522 A188016 Adjacent sequences: A224867 A224868 A224869 * A224871 A224872 A224873 KEYWORD nonn AUTHOR Zak Seidov, Jul 22 2013 STATUS approved

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Last modified August 7 03:39 EDT 2024. Contains 375008 sequences. (Running on oeis4.)