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

1,1

Links

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

Example

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

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 *)

Crossrefs

Cf. A002496, A072858.

Sequence in context: A254759 A139390 A145824 * A145986 A375424 A200992

Adjacent sequences: A076513 A076514 A076515 * A076517 A076518 A076519

Keyword

nonn

Author

Benoit Cloitre, Nov 09 2002

Status

approved