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A062803 Number of solutions to x^2 == y^2 (mod n). 7
1, 2, 5, 8, 9, 10, 13, 24, 21, 18, 21, 40, 25, 26, 45, 64, 33, 42, 37, 72, 65, 42, 45, 120, 65, 50, 81, 104, 57, 90, 61, 160, 105, 66, 117, 168, 73, 74, 125, 216, 81, 130, 85, 168, 189, 90, 93, 320, 133, 130, 165, 200, 105, 162, 189, 312, 185, 114, 117, 360, 121, 122, 273 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

László Tóth, Counting Solutions of Quadratic Congruences in Several Variables Revisited, J. Int. Seq. 17 (2014) # 14.11.6.

FORMULA

a(n) is multiplicative and, for an odd prime p, a(p) = 2*p - 1.

Multiplicative with a(2^e)=e*2^e and a(p^e)=((p-1)*e+p)*p^(e-1) for an odd prime p. - Vladeta Jovovic, Sep 22 2003

MATHEMATICA

f[2, e_] := e*2^e; f[p_, e_] := ((p-1)*e+p)*p^(e-1); a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 10 2020 *)

CROSSREFS

Cf. A086933.

Sequence in context: A047620 A283205 A322916 * A231756 A212591 A153275

Adjacent sequences:  A062800 A062801 A062802 * A062804 A062805 A062806

KEYWORD

nonn,mult,easy

AUTHOR

Ahmed Fares (ahmedfares(AT)my-deja.com), Jul 19 2001

EXTENSIONS

More terms from Vladeta Jovovic, Sep 22 2003

STATUS

approved

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Last modified October 21 20:32 EDT 2020. Contains 337925 sequences. (Running on oeis4.)