A259255 With a(1) = 1, a(n) is the smallest number not already in the sequence such that -1 + Product_{i=1..n} a(i) is a square.

1, 2, 5, 17, 13, 97, 3077, 155333, 147223992353, 182758163483477540989, 634072602906397751091977058984828897557

Offset

1,2

Links

Table of n, a(n) for n=1..11.

Prog

(PARI) v=[1]; n=1; while(n<10^6, s=-1+n*prod(i=1, #v, v[i]); if(issquare(s)&&! vecsearch(vecsort(v), n), v=concat(v, n); n=0); n++); v

Crossrefs

Cf. A094353, A083275.

Sequence in context: A366609 A178198 A005529 * A274903 A206029 A057282

Adjacent sequences: A259252 A259253 A259254 * A259256 A259257 A259258

Keyword

nonn,hard,more

Author

Derek Orr, Jun 22 2015

Extensions

a(9)-a(11) from Giovanni Resta, Jun 22 2015

Status

approved