A109505 Consider the smallest pair of consecutive squarefree numbers (r,s) with gcd(r,s) = n; sequence gives values of r, or -1 if n is not squarefree.

1, 422, 174, -1, 22830, 9216772051242, 234374, -1, -1

Offset

1,2

Comments

a(10) <= 462850319999160398264270. - David A. Corneth, Sep 19 2020

If n is odd then a(n) >= A020754(n-1). If n is even then a(n) >= A020754(2n-1). - Jud McCranie, Sep 30 2020

Links

Table of n, a(n) for n=1..9.

Example

174 is squarefree, 177 is the next squarefree integer, and gcd(174,177) = 3; this is the first pair of consecutive squarefree numbers whose GCD is 3, so a(3)=174. - Jud McCranie, Nov 25 2019

Crossrefs

See A109473, the main entry for this sequence, for more information.

Cf. A020754, A337914, A337915.

Sequence in context: A083193 A340871 A303334 * A109473 A245315 A357890

Adjacent sequences: A109502 A109503 A109504 * A109506 A109507 A109508

Keyword

sign,hard,more

Author

N. J. A. Sloane, Aug 31 2005

Extensions

a(6) corrected by Don Reble. - N. J. A. Sloane, Nov 25 2019

Status

approved