A064461 First row of Pascal's triangle that has n distinct nonsquarefree entries, or -1 if no such row exists.

0, 4, 13, 8, 9, 12, 17, 20, 16, 18, 26, 24, 62, 27, 34, 33, 32, -1, 36, 40, -1, 95, -1, 79, 48, 50, 54, 60, 56, 74, 67, 65, 64, 73, -1, 94, 72, 91, 85, 83, 80, 84, 119, 88, -1, 97, 104, 101, 96, 98, 100, -1, 115, -1, 108, 114, 112, 123, 122, 120, 121, 125, 131

Offset

0,2

Comments

Numbers such that a(n) is -1: 17, 20, 22, 34, 44, 51, ... - Michel Marcus, Mar 05 2014

Links

Table of n, a(n) for n=0..62.

Example

a(2) = 13 because C(13,5) = 3^2*11*13 and C(13,6) = 2^2*3*11*13.

Mathematica

f[ n_ ] := (c = 0; k = 1; While[ k < n/2 + .5, If[ Union[ Transpose[ FactorInteger[ Binomial[ n, k ] ] ] [ [ 2 ] ] ] [ [ -1 ] ] > 1, c++ ]; k++ ]; c); Do[ m = 2; While[ f[ m ] != n, m++ ]; Print[ m ], {n, 0, 16} ]

Prog

(PARI) a(n, v) = {for (i=1, #v, if (v[i] == n, return (i-1)); ); return (-1); } \\ where v is vector A064460; Michel Marcus, Mar 05 2014

Crossrefs

Cf. A064460, A064462, A048276.

Sequence in context: A249120 A170844 A051432 * A046737 A046738 A095324

Adjacent sequences: A064458 A064459 A064460 * A064462 A064463 A064464

Keyword

sign

Author

Robert G. Wilson v, Oct 02 2001

Extensions

Corrected and extended by Michel Marcus, Mar 05 2014

Status

approved