A034901 a(n) is square mod a(i), i < n; a(n) nonsquare; a(1) = 2.

2, 3, 6, 7, 15, 21, 30, 39, 51, 120, 204, 480, 816, 849, 2041, 2185, 4785, 19140, 21505, 43065, 44080, 49504, 59185, 172260, 176320, 178465, 236740, 387585, 443521, 552601, 1774084, 2210404, 2310385, 3991689, 4973409, 5371081, 7096336

Offset

1,1

Links

Table of n, a(n) for n=1..37.

Prog

(PARI) isok(newa, v, n) = {for (k=1, n, if (!issquare(Mod(newa, v[k])), return (0)); ); return (1); }
nextnonsq(n) = my(k=n); while (issquare(k), k++); k;
lista(nn) = {my(v=vector(nn), lasta=2); v[1] = lasta; for (n=2, nn, my(newa = nextnonsq(lasta+1)); while (! isok(newa, v, n-1), newa = nextnonsq(newa+1)); v[n] = newa; lasta = newa; ); v; } \\ Michel Marcus, Sep 25 2020

Crossrefs

Cf. A000037 (nonsquares), A034900, A034902.

Sequence in context: A265394 A125167 A137604 * A343149 A275390 A109976

Adjacent sequences: A034898 A034899 A034900 * A034902 A034903 A034904

Keyword

nonn

Author

David W. Wilson

Status

approved