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A347833
Number of solutions to the congruence (x+1)*x + 4 == 0 (mod A347831(n)).
2
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.
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
Sequence in context: A298642 A243404 A219181 * A260341 A109969 A085035
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang, Sep 15 2021
STATUS
approved