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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. 4
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 (list; table; graph; refs; listen; history; text; internal format)
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: A080511 A132399 A287616 * A100337 A036584 A260453

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

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Last modified June 17 19:10 EDT 2019. Contains 324198 sequences. (Running on oeis4.)