A238336 The first row of Pascal's triangle having exactly n distinct squarefree numbers, or -1 if no such row exists.

0, 2, 5, 7, 13, 11, 15, 44, 53, 46, 59, 23, 43, 278, 191, 143, 79, 119, 187, 62, 47, 221, 214, 1643, 159, 238, 95, 473, 314, 3583, 671, 474, 958, 3071, 5719, 215, 1439, 7423, 1663, 447, 223, 3695, 4346, 4318, 12983, 319, 35069, 5983, 5471, 8567, 959, 3067

Offset

1,2

Links

Table of n, a(n) for n=1..52.

A. Granville and O. Ramaré, Explicit bounds on exponential sums and the scarcity of squarefree binomial coefficients, Mathematika 43 (1996), 73-107, [DOI].

Mathematica

nn = 20; t = Table[-1, {nn}]; found = 0; n = -1; While[found < nn, n++; len = Length[Select[Binomial[n, Range[0, n/2]], SquareFreeQ[#] &]]; If[0 < len <= nn && t[[len]] == -1, t[[len]] = n; found++]]; t

Crossrefs

Cf. A064461, A238337.

Sequence in context: A041975 A042577 A092792 * A083271 A094285 A121218

Adjacent sequences: A238333 A238334 A238335 * A238337 A238338 A238339

Keyword

nonn,more,hard

Author

T. D. Noe, Mar 05 2014

Extensions

Extended by T. D. Noe, Mar 07 2014

Status

approved