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 A100876 Least number of squares that sum to prime(n). 0
 2, 3, 2, 4, 3, 2, 2, 3, 4, 2, 4, 2, 2, 3, 4, 2, 3, 2, 3, 4, 2, 4, 3, 2, 2, 2, 4, 3, 2, 2, 4, 3, 2, 3, 2, 4, 2, 3, 4, 2, 3, 2, 4, 2, 2, 4, 3, 4, 3, 2, 2, 4, 2, 3, 2, 4, 2, 4, 2, 2, 3, 2, 3, 4, 2, 2, 3, 2, 3, 2, 2, 4, 4, 2, 3, 4, 2, 2, 2, 2, 3, 2, 4, 2, 4, 3, 2, 2, 2, 4, 3, 4, 4, 3, 3, 4, 2, 2, 3, 2, 3, 2, 3, 2, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Note that a(n) <= 4 by Lagrange's four-square theorem. - T. D. Noe, Jan 10 2005 Primes 2 and 4k+1 (A002313) require only 2 positive squares; primes 8k+3 (A007520) require 3 positive squares; primes 8k+7 (A007522) require 4 positive squares. LINKS FORMULA a(n) = A002828(prime(n)) - T. D. Noe, Jan 10 2005 EXAMPLE a(2)=3 because 3=1^2+1^2+1^2; a(3)=2 because 5=1^2+2^2; a(4)=4 because 7=2^2+1^2+1^2+1^2. MATHEMATICA SquareCnt[n_] := If[SquaresR[1, n] > 0, 1, If[SquaresR[2, n] > 0, 2, If[SquaresR[3, n] > 0, 3, 4]]]; Table[p = Prime[n]; SquareCnt[p], {n, 150}] (* T. D. Noe, Jan 10 2005, revised Sep 27 2011 *) CROSSREFS Cf. A002828 (least number of squares needed to represent n). Sequence in context: A308566 A288535 A105117 * A089215 A238766 A325239 Adjacent sequences: A100873 A100874 A100875 * A100877 A100878 A100879 KEYWORD nonn AUTHOR Giovanni Teofilatto, Jan 09 2005 EXTENSIONS More terms from T. D. Noe, Jan 10 2005 STATUS approved

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Last modified December 3 09:50 EST 2022. Contains 358517 sequences. (Running on oeis4.)