A347833 Number of solutions to the congruence (x+1)*x + 4 == 0 (mod A347831(n)).

1, 2, 1, 2, 1, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 4, 2, 4, 2, 2, 2, 2, 2, 2, 2, 4, 2, 4, 2, 4, 2, 2, 2, 2, 4, 2, 4, 2, 2, 4, 4, 2, 2, 2, 4, 2, 2, 4, 4, 2, 4, 2, 4, 2, 2, 2, 4, 2, 4, 2, 2, 4, 2, 4, 2, 2, 2, 4, 4, 4, 4, 2, 2

Offset

1,2

Comments

A347832 gives the representatives of these residue classes.

Links

Table of n, a(n) for n=1..78.

Formula

a(n) equals the length of row n of A347832(n).

Prog

(PARI) isok(m) = {my(f=factor(m)); for (k=1, #f~, my(p=f[k, 1]); if ((p==3) || (p==5), if (f[k, 2] > 1, return (0)), if (kronecker(p, 15) != 1, return(0))); ); return (1); } \\ A347831
f(n) = sum(x=0, n-1, Mod(x*(x+1), n) == -4);
lista(nn) = apply(f, select(isok, [1..nn])); \\ Michel Marcus, Oct 23 2021

Crossrefs

Cf. A347831, A347832.

Sequence in context: A298642 A243404 A219181 * A260341 A109969 A085035

Adjacent sequences: A347830 A347831 A347832 * A347834 A347835 A347836

Keyword

nonn,easy

Author

Wolfdieter Lang, Sep 15 2021

Status

approved