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 A256503 Smallest k>=1 such that n^2 + (n+1)^2 + ... + (n+k)^2 is prime or a(n)=0 if there is no such k. 4
 1, 1, 5, 1, 1, 2, 1, 0, 1, 0, 0, 1, 5, 1, 0, 0, 1, 5, 1, 0, 5, 1, 5, 1, 1, 0, 0, 0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 5, 1, 0, 0, 1, 0, 0, 0, 0, 1, 5, 0, 1, 5, 2, 0, 0, 0, 2, 0, 0, 0, 1, 0, 2, 5, 0, 1, 2, 0, 0, 1, 1, 0, 1, 0, 0, 0, 2, 0, 0, 1, 0, 5, 1, 0, 1, 1, 2, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Every term is either 0 or 1 or 2 or 5. a(n)=0 if and only if n is in A256385. LINKS FORMULA 1) if 2n^2+2n+1 is prime, then a(n)=1; 2) if 2n^2+2n+1 is not prime, but 3n^2+6n+5 is prime, then a(n)=2; 3) if 2n^2+2n+1 and 3n^2+6n+5 are both composite numbers, but 6n^2+30n+55 is prime, then a(n)=5; 4) otherwise, a(n)=0. CROSSREFS Cf. A000290, A256385, A089306. Sequence in context: A130511 A320410 A011396 * A036791 A180136 A010129 Adjacent sequences:  A256500 A256501 A256502 * A256504 A256505 A256506 KEYWORD nonn AUTHOR Vladimir Shevelev, Mar 31 2015 EXTENSIONS More terms from Peter J. C. Moses, Mar 31 2015 STATUS approved

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Last modified January 27 10:31 EST 2021. Contains 340461 sequences. (Running on oeis4.)