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 A205526 Least positive integer y such that Kronecker(y^2 - 4, p(n)) == -1 and (x+2)^(p(n)+1) == 5 -+ 2*y (mod p(n), mod x^2 +- y*x + 1). 1
 1, 3, 1, 3, 1, 3, 1, 4, 1, 1, 4, 3, 1, 3, 1, 1, 1, 5, 3, 1, 3, 4, 1, 1, 3, 1, 3, 1, 6, 1, 3, 1, 1, 4, 1, 4, 3, 3, 1, 1, 1, 5, 1, 3, 1, 4, 4, 3, 1, 5, 1, 1, 5, 1, 1, 1, 1, 4, 3, 1, 3, 1, 3, 1, 3, 1, 4, 3, 1, 5, 1, 1, 3, 3, 4, 1, 1, 3, 1, 5, 1, 6, 1, 3, 4, 1, 1, 3, 1, 3, 1, 1, 3, 1, 4, 1, 1, 1, 3, 6, 3, 1, 1, 1, 4, 3, 1, 1, 1, 5, 3, 3, 1, 4, 4, 1, 3, 1, 1, 1, 5, 3, 1, 1, 4, 1, 6, 1, 3, 3, 4, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This is an alternate version of A205531, which should be considered as the main entry. One has A205526(n)=A205531(n) whenever the latter is nonzero. Related to the 4.X Selfridge Conjecture by P. Underwood, which states that p is prime iff such an y exists. Records are [p, y] = [A205532(n), A205534(n)] = [2, 1], [3, 3], [19, 4], [61, 5], [109, 6], [1009, 9], [2689, 11], [8089, 15], [33049, 17], [53881, 21], [87481, 27], [483289, 29], [515761, 35], [1083289, 39], [3818929, 45], ... LINKS P. Underwood, 4.X Selfridge Conjecture (on "Prime Pages" profile), Jan 2012. PROG (PARI) a(n)={n=prime(n); for(y=1, 1e7, kronecker(y^2-4, n)==-1 | next; Mod(x+Mod(2, n), x^2-y*x+1)^(n+1)==5+2*y | next; Mod(x+Mod(2, n), x^2+y*x+1)^(n+1)==5-2*y & return(y))} CROSSREFS Sequence in context: A111736 A330889 A035652 * A233269 A035689 A296082 Adjacent sequences:  A205523 A205524 A205525 * A205527 A205528 A205529 KEYWORD nonn AUTHOR M. F. Hasler, Jan 28 2012 STATUS approved

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Last modified December 3 00:59 EST 2021. Contains 349445 sequences. (Running on oeis4.)