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A076342 a(n) = A076340(A000040(n)), real part of primes mapped as defined in A076340, A076341. 7
2, 4, 4, 8, 12, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 60, 60, 68, 72, 72, 80, 84, 88, 96, 100, 104, 108, 108, 112, 128, 132, 136, 140, 148, 152, 156, 164, 168, 172, 180, 180, 192, 192, 196, 200, 212, 224, 228, 228, 232, 240, 240, 252, 256, 264, 268, 272 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

By definition of the map defined in A076340, A076341: 2->(2,0) and p->((floor(p/4)+floor((p mod 4)/2))*4,2-(p mod 4)) for odd primes p.

Number of solutions to x^2 + y^2 = 1 (mod p). - Lekraj Beedassy, Oct 22 2004

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = p-(-1/p) = p+(-1)^{(p+1)/2} for an odd prime p. {(a/b) stands for the value of the Legendre symbol}. - Lekraj Beedassy, Oct 22 2004

EXAMPLE

A000040(11)=31=(32-1) -> (32,-1), therefore a(11)=32 and A070750(11)=-1.

MAPLE

f:= proc(n) local p;

  p:= ithprime(n);

  if p mod 4 = 1 then p-1 elif p mod 4 = 3 then p+1 else 2 fi

end proc:

map(f, [$1..100]); # Robert Israel, Dec 26 2016

MATHEMATICA

a[1] = 2; a[n_] := With[{p = Prime[n]}, p - JacobiSymbol[-1, p]]; Array[a, 60] (* Jean-Fran├žois Alcover, Feb 01 2018, after Lekraj Beedassy *)

CROSSREFS

Cf. A000040, A070750, A076340, A076341.

Sequence in context: A055946 A130124 A265417 * A135268 A245619 A131771

Adjacent sequences:  A076339 A076340 A076341 * A076343 A076344 A076345

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Oct 08 2002

STATUS

approved

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Last modified August 23 22:45 EDT 2019. Contains 326254 sequences. (Running on oeis4.)