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Search: id:A081485
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| A081485 |
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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. |
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+0
4
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| 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; listen)
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OFFSET
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1,3
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COMMENT
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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.
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LINKS
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Franklin T. Adams-Watters, Rows n=1..80 of triangle, flattened
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EXAMPLE
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Triangle begins
1
1 3
1 2 3
1 3 5 7
1 2 3 5 19
1 3 5 7 13 19
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PROGRAM
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Contribution from Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), 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)
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CROSSREFS
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Cf. A081486, A081487, A081488.
Sequence in context: A079723 A080511 A132399 this_sequence A100337 A036584 A165084
Adjacent sequences: A081482 A081483 A081484 this_sequence A081486 A081487 A081488
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KEYWORD
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nonn,tabl
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 24 2003
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EXTENSIONS
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Corrected and extended by David Wasserman (wasserma(AT)spawar.navy.mil), Jun 03 2004
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