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 A004144 Nonhypotenuse numbers (squares that are not the sums of 2 distinct nonzero squares). (Formerly M0542) 41
 1, 2, 3, 4, 6, 7, 8, 9, 11, 12, 14, 16, 18, 19, 21, 22, 23, 24, 27, 28, 31, 32, 33, 36, 38, 42, 43, 44, 46, 47, 48, 49, 54, 56, 57, 59, 62, 63, 64, 66, 67, 69, 71, 72, 76, 77, 79, 81, 83, 84, 86, 88, 92, 93, 94, 96, 98, 99, 103, 107, 108, 112, 114, 118, 121, 124, 126, 127 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers with no prime factors of form 4*k+1. m is a term iff A072438(m) = m. Density 0. - Charles R Greathouse IV, Apr 16 2012 A005089(a(n)) = 0. - Reinhard Zumkeller, Jan 07 2013 Closed under multiplication. Primitive elements are 2 and the primes of form 4*k+3. - Jean-Christophe HervĂ©, Nov 17 2013 REFERENCES S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 98-104. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS T. D. Noe, Table of n, a(n) for n = 1..1000 S. R. Finch, Landau-Ramanujan Constant D. Shanks, Non-hypotenuse numbers, Fib. Quart., 13:4 (1975), pp. 319-321. Eric Weisstein's World of Mathematics, Pythagorean Triple MATHEMATICA fQ[n_] := If[n > 1, First@ Union@ Mod[ First@# & /@ FactorInteger@ n, 4] != 1, True]; Select[ Range@ 127, fQ] PROG (PARI) is(n)=n==1||vecmin(factor(n)[, 1]%4)>1 \\ Charles R Greathouse IV, Apr 16 2012 (Haskell) import Data.List (elemIndices) a004144 n = a004144_list !! (n-1) a004144_list = map (+ 1) \$ elemIndices 0 a005089_list -- Reinhard Zumkeller, Jan 07 2013 CROSSREFS Complement of A009003. Cf. A072437. Sequence in context: A209921 A268377 A201010 * A124391 A200381 A050118 Adjacent sequences:  A004141 A004142 A004143 * A004145 A004146 A004147 KEYWORD nonn AUTHOR EXTENSIONS More terms from Reinhard Zumkeller, Jun 17 2002 STATUS approved

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Last modified March 23 02:58 EDT 2019. Contains 321422 sequences. (Running on oeis4.)