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 A238534 Number of solutions to gcd(u^2 + v^2 + w^2 + x^2 + y^2 + z^2, n) = 1 with u, v, w, x, y, z in [0,n-1]. 6
 1, 32, 504, 2048, 12400, 16128, 101136, 131072, 367416, 396800, 1611720, 1032192, 4453488, 3236352, 6249600, 8388608, 22713088, 11757312, 44576280, 25395200, 50972544, 51575040, 141611184, 66060288, 193750000, 142511616, 267846264, 207126528, 574288624 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Robert Israel, Table of n, a(n) for n = 1..2000 (first 100 terms from Giovanni Resta) C. Calderón, J. M. Grau, and A. Oller-Marcén, Counting invertible sums of squares modulo n and a new generalization of Euler totient function, arXiv:1403.7878 [math.NT], 2014. C. Calderón, J. M. Grau, and A. Oller-Marcén, Counting invertible sums of squares modulo n and a new generalization of Euler totient function, Publicationes mathematicae 87(1-2) (2015), 133-145. FORMULA Multiplicative with a(2^e) = 2^(6*e-1), a(p^e) = (p - 1)*p^(6*e - 4)*(p^3 - (-1)^(3*(p-1)/2)) for odd prime p. - Andrew Howroyd, Aug 07 2018 MAPLE f:= proc(n) local i, j, k, S1, S2,  S4,  S6, G;   G:= select(t -> igcd(t, n)=1, [\$1..n-1]);   S1:= Array(0..n-1);   for i from 0 to n-1 do j:= i^2 mod n; S1[j]:= S1[j]+1; od;   S2:= Array(0..n-1);   for i from 0 to n-1 do     for j from 0 to n-1 do       k:= i^2 + j mod n;       S2[k]:= S2[k]+S1[j];   od od:   S4:= Array(0..n-1);   for i from 0 to n-1 do     for j from 0 to n-1 do       k:= i + j mod n;       S4[k]:= S4[k]+S2[i]*S2[j];   od od:   S6:= Array(0..n-1);   for i from 0 to n-1 do     for j from 0 to n-1 do       k:= i + j mod n;       S6[k]:= S6[k]+S4[i]*S2[j];   od od:   add(S6[i], i=G); end proc: f(1):= 1: map(f, [\$1..100]); # Robert Israel, Mar 05 2018 MATHEMATICA g[n_, 6] := g[n, 6] = Sum[If[GCD[u^2+v^2+w^2+x^2+y^2+z^2, n] == 1, 1, 0], {u, n}, {v, n}, {w, n}, {x, n}, {y, n}, {z, n}]; Table[g[n, 6], {n, 1, 12}] PROG (PARI) a(n)={my(p=lift(Mod(sum(i=0, n-1, x^(i^2%n)), x^n-1)^6)); sum(i=0, n-1, if(gcd(i, n)==1, polcoeff(p, i)))} \\ Andrew Howroyd, Aug 06 2018 (PARI) a(n)={my(f=factor(n)); prod(i=1, #f~, my([p, e]=f[i, ]); if(p==2, 2^(6*e-1), (p - 1)*p^(6*e - 4)*(p^3 - (-1)^(3*(p-1)/2))))} \\ Andrew Howroyd, Aug 07 2018 CROSSREFS Cf. A227499, A238533, A239441. Sequence in context: A220735 A010948 A022627 * A297091 A271577 A116003 Adjacent sequences:  A238531 A238532 A238533 * A238535 A238536 A238537 KEYWORD nonn,mult AUTHOR José María Grau Ribas, Feb 28 2014 EXTENSIONS a(16)-a(29) from Giovanni Resta, Mar 05 2014 STATUS approved

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Last modified August 9 12:05 EDT 2022. Contains 356026 sequences. (Running on oeis4.)