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A173662 Triangle read by rows: R(n,k)= semiprime(n) mod semiprime(k), 0<k<=n. 0
0, 2, 0, 1, 3, 0, 2, 4, 1, 0, 2, 2, 5, 4, 0, 3, 3, 6, 5, 1, 0, 1, 3, 3, 1, 7, 6, 0, 2, 4, 4, 2, 8, 7, 1, 0, 1, 1, 7, 5, 11, 10, 4, 3, 0, 2, 2, 8, 6, 12, 11, 5, 4, 1, 0, 1, 3, 6, 3, 5, 3, 12, 11, 8, 7, 0, 2, 4, 7, 4 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row sums are 0, 2, 4, 7, 13, 18, 28,...

LINKS

Table of n, a(n) for n=1..70.

EXAMPLE

0,

2,0;

1,3,0;

2,4,1,0;

2,2,5,4,0;

3,3,6,5,1,0;

1,3,3,1,7,6,0;

2,4,4,2,8,7,1,0;

MATHEMATICA

SemiprimeQ[n_Integer] := If[Abs[n]<2, False, (2==Plus@@Transpose[FactorInteger[Abs[n]]][[2]])]; sp = Select[Range[100], SemiprimeQ]; Flatten[Table[Mod[sp[[n]], sp[[Range[n]]]], {n, Length[sp]}]]

CROSSREFS

Cf. A001358, A173655.

Sequence in context: A022880 A128097 A328096 * A263406 A257230 A172026

Adjacent sequences:  A173659 A173660 A173661 * A173663 A173664 A173665

KEYWORD

nonn,tabl,easy

AUTHOR

Juri-Stepan Gerasimov, Nov 28 2010

EXTENSIONS

46th term corrected by D. S. McNeil, Nov 24 2010

STATUS

approved

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Last modified October 25 13:27 EDT 2021. Contains 348252 sequences. (Running on oeis4.)