A081485 Triangle read by rows in which the n-th row contains the smallest set of n coprime numbers with a sum which is a multiple of n.

1, 1, 3, 1, 2, 3, 1, 3, 5, 7, 1, 2, 3, 5, 19, 1, 3, 5, 7, 13, 19, 1, 2, 3, 5, 7, 11, 13, 1, 3, 5, 7, 11, 13, 17, 23, 1, 2, 3, 5, 7, 11, 13, 17, 31, 1, 3, 5, 7, 11, 13, 17, 19, 23, 31, 1, 2, 3, 5, 7, 11, 13, 17, 19, 23, 31, 1, 3, 5, 7, 11, 13, 17, 19, 23, 29, 41, 47, 1, 2, 3, 5, 7, 11, 13, 17

Offset

1,3

Comments

In the row for 6 the fifth term is 13 and not 11 as this forces the sixth term divisible by (not coprime to 3) 3. For even n all the terms have to be odd. This sequence set should exhibit some interesting properties and needs attention.

Links

Franklin T. Adams-Watters, Rows n=1..80 of triangle, flattened

Example

Triangle begins
1
1 3
1 2 3
1 3 5 7
1 2 3 5 19
1 3 5 7 13 19

Prog

Contribution from Franklin T. Adams-Watters, Apr 09 2009: (Start)
(PARI) arow(n) = {local(v, t, p, r);
if(n<=3, return(if(n==2, [1, 3], if(n==3, [1, 2, 3], [1]))));
v=vector(n); v[1]=1; v[2]=if(n%2==0, 3, 2); t=v[2]+1;
for(i=3, n-2, v[i]=nextprime(v[i-1]+1); t+=v[i]);
p=nextprime(v[n-2]+1);
while(gcd(t+p, n)>1, p=nextprime(p+1));
v[n-1]=p; t+=p; r=p\n*n-t%n;
while(r<=p, r+=n);
while(!isprime(r), r+=n);
v[n]=r; v} (End)

Crossrefs

Cf. A081486, A081487, A081488.

Sequence in context: A132399 A287616 A371101 * A307693 A100337 A036584

Adjacent sequences: A081482 A081483 A081484 * A081486 A081487 A081488

Keyword

nonn,tabl

Author

Amarnath Murthy, Mar 24 2003

Extensions

Corrected and extended by David Wasserman, Jun 03 2004

Status

approved