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 A173472 Numbers k such that exactly one of prime(k)^2 - 2 and prime(k)^2 + 2 is prime. 0
 1, 3, 4, 6, 8, 10, 12, 14, 15, 18, 20, 24, 27, 28, 31, 32, 34, 40, 43, 47, 48, 51, 52, 55, 62, 65, 68, 72, 82, 86, 87, 91, 94, 99, 100, 104, 107, 111, 119, 123, 128, 129, 130, 132, 133, 134, 135, 139, 141, 150, 152, 170, 172, 177, 180, 182, 191, 200, 202, 209, 211, 214 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Essentially the same as A137291. LINKS EXAMPLE a(1)=1 because prime(1)^2 - 2 = 2 is prime and prime(1)^2 + 2 = 6 is composite. MAPLE isA173472 := proc(n) local p, pplus, pmin ; p := ithprime(n) ; pmin := isprime(p^2-2) ; pplus := isprime(p^2+2) ; if pmin <> pplus then return true; else return false; end if; end proc: for n from 1 to 300 do if isA173472(n) then printf("%d, ", n) ; end if; end do ; # R. J. Mathar, Feb 21 2010 CROSSREFS Cf. A137291. Sequence in context: A206818 A191262 A184736 * A058992 A051755 A092535 Adjacent sequences:  A173469 A173470 A173471 * A173473 A173474 A173475 KEYWORD nonn,less AUTHOR Juri-Stepan Gerasimov, Feb 19 2010 EXTENSIONS More terms from R. J. Mathar, Feb 21 2010 Edited by Charles R Greathouse IV, Mar 24 2010 STATUS approved

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Last modified June 16 10:03 EDT 2019. Contains 324152 sequences. (Running on oeis4.)