A173556 - OEIS

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A173556

Triangle T(n,m) = (prime(n)-1)*(prime(m)- 1) mod 8 read by rows.

1, 2, 4, 4, 0, 0, 6, 4, 0, 4, 2, 4, 0, 4, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 0, 4, 4, 0, 0, 4, 6, 4, 0, 4, 4, 0, 0, 4, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 4, 0, 4, 4, 0, 0, 4, 4, 0, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 0, 4, 4, 0, 0, 4, 4, 0, 4, 0, 0, 4, 6

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OFFSET

1,2

COMMENTS

Row sums are: 1, 6, 4, 14, 14, 4, 0, 18, 26, 4,...

LINKS

Table of n, a(n) for n=1..106.

FORMULA

t(n,m)=Mod[(Prime[n] - 1)*(Prime[m] - 1), 8]

EXAMPLE

The triangle (prime(n)-1)*(prime(m)-1) starts

2,4 ;

4,8,16 ;

6,12,24,36 ;

10,20,40,60,100 ;

12,24,48,72,120,144 ;

16,32,64,96,160,192,256 ;

and reduced mod 8, T(n,m) starts

2, 4;

4, 0, 0;

6, 4, 0, 4;

2, 4, 0, 4, 4;

4, 0, 0, 0, 0, 0;

0, 0, 0, 0, 0, 0, 0;

2, 4, 0, 4, 4, 0, 0, 4;

6, 4, 0, 4, 4, 0, 0, 4, 4;

4, 0, 0, 0, 0, 0, 0, 0, 0, 0;

MATHEMATICA

t[n_, m_] = Mod[(Prime[n] - 1)*(Prime[m] - 1), 8];

Table[Table[t[n, m], {m, 1, n}], {n, 1, 10}];

Flatten[%]

CROSSREFS

Sequence in context: A370635 A258371 A111172 * A247554 A198786 A176531

Adjacent sequences: A173553 A173554 A173555 * A173557 A173558 A173559

KEYWORD

nonn,tabl,easy

AUTHOR

Roger L. Bagula, Feb 21 2010

EXTENSIONS

Standardized nomenclature - the Assoc. Editors of the OEIS, Feb 24 2010

STATUS

approved