A145872 - OEIS

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A145872

Smallest k such that k^2+1 is divisible by A002144(n)^8.

110443, 6826318, 3379649772, 61012922706, 1019349744435, 287369842623, 11331029931180, 71294762793847, 239822883201307, 923990886302412, 2369608176604944, 3156215819652023, 521749964271465, 2026364722410364

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

a(1) = 110443 since A002144(1) = 5, 110443^2+1 = 12197656250 = 2*5^8*13*1201 and for no k < 110443 does 5^8 divide k^2+1. a(3) = 3379649772 since A002144(3) = 17, 3379649772^2+1 = 11422032581379651985 = 5*13*17^8*97*259697 and for no k < 3379649772 does 17^8 divide k^2+1.

PROG

(PARI) {e=8; forprime(p=2, 40, if(p%4==1, q=p^e; m=q; while(!issquare(m-1, &n), m=m+q); print1(n, ", ")))}

CROSSREFS

Cf. A002144 (primes of form 4n+1), A002313 (-1 is a square mod p), A059321, A145296, A145297, A145298, A145299, A145871, A145873.

Sequence in context: A122240 A250591 A187114 * A254853 A250533 A251191

Adjacent sequences: A145869 A145870 A145871 * A145873 A145874 A145875

KEYWORD

nonn

AUTHOR

Klaus Brockhaus, Oct 22 2008

EXTENSIONS

More terms from Klaus Brockhaus, Nov 12 2008

STATUS

approved