A076516 Primes p such that (p-1) and the period length of 1/p are both squares.

5, 17, 101, 257, 577, 1297, 3137, 5477, 7057, 12101, 13457, 14401, 15377, 24337, 25601, 30977, 33857, 41617, 42437, 44101, 50177, 52901, 55697, 57601, 62501, 65537, 69697, 72901, 80657, 98597, 106277, 122501, 147457, 164837, 184901

Offset: 1

Author

Benoit Cloitre, Nov 09 2002

Keywords

• nonn

Examples

			(17-1) = 16 is square and 1/17=0.0588235294117647(0588...) with a decimal period length = 16, square, hence 17 is in the sequence
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..230

Crossrefs

Cf. A002496, A072858.

Programs

Mathematica

bsQ[n_]:=IntegerQ[Sqrt[n-1]]&&IntegerQ[Sqrt[Length[Flatten[ RealDigits[ 1/n][[1]]]]]]; Select[Prime[Range[2,17000]],bsQ] (* Harvey P. Dale, May 30 2013 *)