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 A193746 Smallest k such that k*n^2 +1 is an n-th power. 3
 1, 2, 7, 5, 311, 434, 42799, 90075, 12345679, 34867844, 6140565047, 1695421, 4696537119847, 20088655029078, 5124095576030431, 25657845139503479, 7563707819165039903, 43404581642184336392, 14523213296398891966759 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE a(9) = 12345679 because 12345679*9^2+1 = 1000000000 = 10^9. MATHEMATICA a={}; Do[k = 2; While[ !IntegerQ[(k^n - 1)/n^2], k++ ]; AppendTo[a, (k^n-1)/n^2], {n, 1, 20}]; a PROG (PARI) a(n)=my(k); while(!ispower(k++*n^2+1, n), ); k \\ Charles R Greathouse IV, May 15 2013 CROSSREFS Sequence in context: A152555 A094360 A051757 * A070524 A021366 A135155 Adjacent sequences:  A193743 A193744 A193745 * A193747 A193748 A193749 KEYWORD nonn,changed AUTHOR Michel Lagneau, Aug 03 2011 STATUS approved

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Last modified May 22 17:33 EDT 2013. Contains 225559 sequences.